MathJax

Sunday, February 16, 2014

Making It Easier For Heavy People To Pedal Up Hills

In bicycle racing, big guys win the sprints on the flat because they have more power and the slight increase in rolling resistance from the extra weight doesn't use much power. The climbers however, are always tiny because human power output doesn't increase proportionally with weight even when the extra weight is all muscle. For many non racers that extra weight is mainly fat which is always a hindrance. They may be able stay with their colleagues on the flat but on a hill they'll be dropped. The usual (and best) strategy is to lose the fat but another solution is to use some assist to carry the extra load up the hill. People sometimes spend thousands of dollars to carry just one or two kilos less bicycle weight up hills and a little assist would be a cheaper alternative.

The goal is to make hills as easy to climb for heavy people as light people or alternatively to make hills less steep even to the point of requiring the same effort as riding on the flat. Say you weigh 90 kg but your riding colleagues way 70 kg and have expensive bikes that are 3 kg lighter. You want enough extra power to carry 23 kg up the hill so you can keep up with them. If you add enough power to carry your weight plus the bike weight, perhaps 12 kg, equating to 102 kg in the example case, then riding up a hill will feel the same as riding on the flat.

The extra power to achieve this is supplied by a motor and to know how much power to request from the motor requires knowing the weight of the rider, the weight of the bike, the speed of the bike and the grade of the hill. Three of these parameters are easily determined but the grade is more difficult.

Barometers can measure height change without calibration using the hypsometric equation. Constant temperature can be assumed to remove the need for a temperature sensor. This increases error but eliminates error due to inaccurate temperature sensing. Air temperature sensing is difficult because the sun can heat the sensor housing. A change in sunlight levels from cloud or sun direction as the bike changes direction can cause the housing to change temperature while external air temperature remains the same.

Measuring grade requires the change in pressure to measure the height change plus the distance travelled between pressure measurements to get the grade. This is how the IpBike app estimates grade. Normally distance is measured using wheel revolutions but I think it will use GPS distance in the absence of wheel sensors. So a barometer would do the job except that you need a reasonable height change which takes a while on a grade. This would mean no help from the motor at the start of the hill and extra motor power after the hill had already passed.

Alternatively an accelerometer can measure the grade with a fast response. This overcomes the problems of the barometer but introduces more. An accelerometer will respond to changes in speed as well as grade. Braking will look like descending and reduce assist and accelerating will increase assist which is  good because the motor will also compensate for the heavier rider during acceleration. Longitudinal vibration will be sensed and may require a little low pass filtering. A single axis accelerometer has to be aligned with the direction of motion and be perpendicular to gravity but this is not practical to do. The readings from a three axis accelerometer can be rotated to match this alignment:-

\(\begin{equation} Acceleration_T = a(A_x- K_a)+b(A_y- K_b)+c(A_z- K_z) \end{equation}\) where \(\begin{equation} \text{$Acceleration_T$}\\ \end{equation}\) is acceleration in the direction of travel, \(\begin{equation} \text{$K_a, K_b$ and $K_z$}\\ \end{equation}\)are accelerations due to gravity in the particular axis direction, \(\begin{equation} \text{$A_x, A_y$ and $A_z$}\\ \end{equation}\) are measured accelerations and \(\begin{equation} \text{$a, b$ and $c$}\\ \end{equation}\) are the components of a unit vector in the direction of travel in the coordinate system of the accelerometer.
\(\begin{equation} \text{$K_a, K_b$ and $K_z$}\\ \end{equation}\) are calculated as the average of a three axis accelerometer over a long enough period while riding. They can be calculated as a moving average over a period of minutes while travelling faster than 10 km/h but will gradually rotate when climbing a hill to match the grade.

Lifting the front of the bike while stationary so that it rotates through about 30-45 degrees and sampling the accelerometers will give a second vector. Taking the cross product of this and the gravity vector defines an axis about which the bicycle rotates when it climbs a hill. This measurement and calculation should only need to be done once as a slight change in sensor rotation about the bike's vertical axis will produce only a small error in the final result. Taking the cross product of the rotation axis with the gravitational vector gives a third vector normal to the other two and therefore in the direction of travel. The scaler components of this vector after normalising provides the values \(\begin{equation} \text{$a, b$ and $c$.}\\ \end{equation}\) Using Newtons second law, the force required to counteract this acceleration along the grade produced by gravity is:-
\(\begin{equation} F= m \times Acceleration_T \end{equation}\) where \(\begin{equation} \text{m}\\ \end{equation}\) is the mass we wish the motor to carry up the hill and the power required to do it is calculated as \(\begin{equation} Power = F \times Speed \end{equation}\) Motor power controlled with this sensor would give immediate help at the start of a grade but in a long hill the power would fade over time.

The barometer is slow to respond but more accurate over time and the accelerometer that self calibrates is responsive but inaccurate over time. Fusing the two sensor outputs gives the best result and this can be done with a simple complementary filter or kalman filter . The assumption that the measurements are corrupted by stationary white noise produces a stationary kalman filter that is identical in form to the complementary filter according to a comparison of complementary and kalman filtering for combining measurements of vertical acceleration and barometric vertical velocity to obtain an estimate of vertical velocity.

In inertial measurement units gyroscopes are often used for sensing rotation but for this case do not add useful grade information.

Tuesday, February 11, 2014

What Killed Noelene and Yvana Bischoff?

Surely not food poisoning.

Following reports that an Australian woman Noelene Bischoff and her 14 year old daughter Yvana died in Bali after falling ill only hours after checking in to room 7 at the Padang Bai Resort, I was curious.

Food poisoning was suspected but I've frequently been ill after eating in Bali and couldn't imagine, not just one, but two people dying  from food poisoning within seven hours of becoming unwell? So I visited the Padang Bai Resort.

After first seeming to know nothing of the incident, as she'd been off that day, the lady on reception advised she was unaware which room they had become sick in. When asked specifically for room 7 she advised it was unavailable but we could have room 6. I'd already seen 7 was unoccupied but she said it was booked.



Padang Bai is a small harbour in Bali from which boats leave to neighbouring Lombok and which features diving, snorkeling and a modest coral reef.



Traders along the waterfront were confident that nothing bad had occurred in Padang Bai, suggesting the  Bischoffs had become ill elsewhere and merely arrived in Padang Bai before the effects became severe. They were also sure the fish served in Padang Bai was healthy as it was caught locally. In press reports the resort manager Mr Bareato had also said the resort buys fresh fish from local fishermen each day. The enthusiasm of locals to maintain the reputation of their community I've found common in Bali, as well as a tendency to blame Javanese when there is trouble. This attitude minimises robbery and violence, as mostly people are looking out for visitors which may in part, stem from recollections of economic devastation in the wake of the bombings. A terrible time for locals, but a period of heavily discounted abundance for visitors that weren't discouraged.

Twelve hours before their deaths, Sunshine Coast mum and daughter Noelene and Yvana Bischoff laughed and joked with waitstaff over a seafood lunch in Ubud and this meal was thought unlikely to have been related to their demise.

Just metres from room 7 is the Buddha Restaurant which the lady on reception had advised was a separate business to the hotel. It was here they ate dinner around 7 pm. So we tried it for lunch.



We asked the waiter about the Bischoffs but he knew nothing about the incident. The press reported the Bischoff's had ordered mahi mahi fish, chicken curry and vegetarian pizza. Just six and a half hours after the meal, Noelene was dead. It was the mahi mahi fish which doctors say is the main suspect.

A day later another Australian, Heath Barclay, fell ill five hours after eating a ham pizza. A Facebook friend mentioned the Bischoffs, "I then check the net and to my horror I had eaten at the same place and had fallen violently ill," Mr Barclay said. "With the police [crime scene] tape in full view of my room at the hotel it was a living hell – I thought I could be next." The 34-year-old plasterer rushed himself to a Denpasar hospital where he was put on an intravenous drip for nine hours. "I was blood tested and told I had severe dehydration and a bacterial infection from food," he said. "I don't really know what would have happened if I didn't go to hospital. If it was the same thing, I can't imagine how terrible it would have been for a 14-year-old girl." However, I can imagine his colleagues on the building site having fun comparing his reaction to that of a 14-year-old girl. Of course it wasn't "the same thing", just the usual unpleasantness of food poisoning combined with the uncertainty of where it originated when he, as I usually have done, ate in more than one place over the previous couple of days. However, it raised suspicions of the pizza and the cleanliness of the kitchen. I glanced in the kitchen and it looked spotless and better equipped than most Bali restaurants. I asked the chef about the Bischoffs but she said she knew nothing and had been rostered off that night. Most staff in Bali work punishing 10 - 12 hour shifts, six days a week so you can be pretty confident of meeting someone that works in a business by turning up at any random time. Padang Bai Resort seems far more generous with leave provisions than most or perhaps we were unlucky. Like Heath Barclay, so far we'd learned nothing more than what had been in the papers.

At lunch Jarrod, in the foreground, couldn't be persuaded from his perennial favourite, sweet and sour pork. Jenny, on the right ordered the vegetarian pizza, but it was only available after 6 pm. Not desiring chicken curry, she settled on leek and potato soup. I requested the mahi mahi (pictured below).



Jenny reported the soup tasted as good as it looked.



The mahi mahi was served with chips and a side salad. It too was lovely. Following a pleasant lunch we went snorkelling and sightseeing. There were no ill effects.



The sudden and mysterious death of two family members was undoubtedly distressing. ‘‘We want the truth,’’ the family spokesperson said. ‘‘We want to know if it was an accident, or if it wasn't an accident. Were they poisoned, or was it something else? ... "We’re worried that there will be a cover-up if the autopsy is done in Bali." Indonesian authorities respected the Bischoff family's request and allowed the bodies to be returned home for autopsy.

A colleague suggested it was probably medication administered in response to initial symptoms that was the culprit but we'd left Bali, none the wiser. Eventually the preliminary autopsy finding was that they died from a combination of food poisoning and existing medical conditions after they ate fish". It was reported that "Malcolm Bischoff, Noelene's brother, said it appeared they both suffered from scombroid food poisoning that, coupled with their asthma and, in Noelene's case, migraine medication had formed a fatal cocktail." My colleague hadn't got it quite right but it was a prescient observation.

Malcolm Bischoff stated "I'm sure we wouldn't have got that answer if the autopsies had been held over there [in Bali]" I'm not so sure, but the Indonesian authorities were wise because Malcolm would likely have been sceptical of the same findings from them. Having accepted the results, Malcolm said "scombroid food poisoning can result from eating spoiled fish, meaning the restaurant's preparation could have made no difference". This defence of the restaurant might be helpful as there was only one other patron having lunch when we were there. He hadn't heard of the Bischoffs and, better informed, some of my party would have preferred to eat elsewhere.

According to the Courier Mail, "scombroid food poisoning occurs when fish like tuna, mackerel, sardines and mahi mahi, is left in temperatures over 5 degrees. After the fish has died, naturally-occurring bacteria can then convert the amino acid histidine into the toxic histamine which can cause severe, allergy-like symptoms." Histamine is not destroyed by normal cooking temperatures, so even properly cooked fish can be affected.

While the autopsy is not yet finalised it seems that the Bischoffs were unlucky. The other people that ate the same fish included the resort manager Giovanni Bareato. They probably didn't have the complicating factors and scombroid concentration varies in different parts of the flesh.  None reported ill effect.

Despite the confidence of the traders that no one from Padang Bai was involved, it does implicate the fisherman who supplied the fish. Had the fish been refrigerated there would not have been scombroid and I'm surprised I've not seen this angle pursued. I don't know the practises in Padang Bai but I've seen fisherman elsewhere in Indonesia selling their daily catch straight from the boat without ice or refrigeration. Convincing fishermen of a need to change this practice is probably a difficult task but, as with Heath Barclay and the Bali bombings, human reaction to tragedy is rarely nuanced, tending to indifference or panic. I'm sure the traders of Padang Bai want to avoid the latter and another scombroid death might provoke it, even though motorbikes is the more common source of tragedy.

Thursday, February 6, 2014

Vernelli Road, NSW - A Secret Public Road

Well it would be a secret if not for Google maps suggesting it as a route from Queanbeyan to Araluen. 

Not far from Canberra in NSW, Australia is an intersection of Gumms road and Vernelli road. Gumms road is a through road but from Vernelli road it is disguised as a gated farm entrance. It is a region where it seems easy to imagine that intergenerational incest could remain hidden among the "smaller farms, used increasingly as hobby farms or boltholes for those on the fringes of society".


View Larger Map

Coming from Gumms road, turning right on Vernelli road takes you to Harold's Cross road but turning left is more interesting, the route of a songline. A songline is a path across the land originating from the dreamtime known only to insiders, usually Indigenous Australians of past generations. To outsiders they are invisible and in my youth I'd found the concept difficult to grasp. What I couldn't see, didn't seem real but nowadays I find it fascinating that what people see is hugely influenced by their frame of reference. Traditional songlines are recorded in song and markings, noticeable only by the group, but modern day songlines, also  known only by insiders are recorded in apps like Strava and Google maps. They exist only within a context, can be overlapping and may have no physical indicators.


A GPS track along the almost secret 7 km section of Vernelli road. There are two wadable water crossings, numerous gates and some steep sections.

Turning left, the dirt road with many gates services only three houses. Vernelli road becomes impassable to normal vehicles as it approaches the  third house, 1.1 km from Gumms road. It is a lovely house, off the grid and secluded by trees just above Bourkes creek. It's as hidden as it is possible for a house to be and was only visible looking backward from the creek. Beyond the creek there is only some wheel ruts and after a while they fade as well. I was here on a bicycle, fortunately mountain style, because Google maps had suggested it as a route from Queanbeyan to Araluen.

However, without the GPS tracking live on a map as I rode I wouldn't have believed it was a road or been able to follow it. On the ground there is sometimes no indication which way to travel, though in places there is cuttings and grade smoothing, indicating it has been a substantial road in the past and in others there is a few metres of  trees separating the road from surrounding paddocks. These are the physical evidence confirming this songline, recorded in cyberspace.


A view down Vernelli road which passes between the trees in the centre of the image. It is taken from the location indicated in the GPS track image above. Grass growing in the wheel tracks indicates the absence of regular traffic.

There are two Strava sections labelled Vernelli (Road/Rd) Climb. The most popular with 20 riders starts in Gumms road, turns right into Vernelli Road and provides a route to Cooma road that is more substantial but longer than the route I followed which Strava records just 3 riders traversing. Without any physical evidence, an observer without Strava  would have no idea this songline exists, yet the creator (not me) and a few insiders know I'm the king of this mountain, probably the only one I'll ever rule.  These insiders can form a whole community that is invisible to non members. Another cyclist is recorded  coming this way, travelling from Wollongong to Melbourne in another instantiation of modern songlines; cycling routes. Perhaps Vernelli road also follows an Aboriginal songline as; being a short route meandering along ridge lines to the Shoalhaven river, it fits many of the criteria.

If you're passing through then Vernelli road, down to Cooma road, is an interesting path which you would never find without becoming an insider but for those on their own, don't get injured as it might be weeks before another insider comes by.

Thursday, January 3, 2013

A Stealthy Motor To Cycle Fast

My suggestion that low power assist is all you want received support and scepticism in a discussion at Endless Sphere. Having formed the view you don't need much help to cycle fast I'm wondering how it can best be done and wish to select a motor and model some scenarios.

What's Out There?

The Gruber Assist, shown in Figure 1, provides a high cost, low power solution that is visually stealthy enough for Fabian Cancellara to be accused of using it during Paris Roubaix and the Tour of Flanders but too noisy for it to be true. Detailed performance information is unavailable but reviews are generally enthusiastic. Negatives reported are 50% efficiency and simple on/off control.

Figure 1: The Gruber Assist is a stealthy 100W output motor that resides in the seat tube.
Bosch mid drive motors have integrated control and display, use pedal torque sensors and offer several operation modes. They appear close to ideal but I'd prefer a mobile phone as the display device, at 4 kg they are heavier than some alternatives, they need a frame designed to fit, and the control algorithms are not published and can't be altered or integrated into cycling tracking applications. Some other mid drive e-bikes are available, like the low cost Aseako/Zoco Rossa.

Friction drive, shown in Figure 2, provides an alternative using small, high speed RC motors but the transmission losses driving the tyre are probably high.

Figure 2: A lightweight friction drive.

Other alternatives are hub drives which are either direct drive or the lighter less powerful geared motors.

Albert van Dalen has done an investigation of bike motors that focuses on efficiency and compares them on weight vs rated power.

Silence Is Beautiful

Modern bicycle motors are brushless DC with six step trapezoidal control explained in this video. Controllers are cheap, from about US$18, but produce motor torque ripple that is often audible. For little additional expense, controllers could use better algorithms to eliminate noise. Figure 3 shows an example of noise reduction in a direct drive hub motor using sinusoidal control.


Figure 3: An example of noise reduction achieved in a direct drive hub motor with sinusoidal control.
There seems to be a gap in the market as only trapezoidal controllers are commercially available.

Torque ripple is avoided by rotating the magnetic flux vector so that it is always perpendicular the magnetic flux vector of the spinning magnets which can be achieved with field oriented control. In contrast to applications like washing machines, torque loads on e-bike motors vary slowly and typical e-bike motors produce sinusoidal back EMFs1. Under these circumstances the simpler sinusoidal control generates the same output as field oriented control.

Field oriented control is often suggested as a means of increasing motor efficiency. In a simulation Johan Astrom2 found only a marginal efficiency improvement with an optimal control scheme over trapezoidal control for a 375 W motor because a non perpendicular magnetic vector mostly acts to store and release energy in different parts of the cycle.

Geared motors can also produce gear noise. The lightweight Tongxin/Keyde hub motor uses rollers rather than gears which is reported as effective for motor silencing but may increase gearbox friction losses.

Regulation

Previously, unregistered electric bikes in Australia were required to "be able to prove that the motor output is not more than 200 watts" but there were no restrictions on how that power could be used. Recently the European standard EN 15194:2009 was introduced as an alternative which allows motors rated up to 250 watts continuous while requiring riders to pedal at speeds above 6 km/h (clause 4.2.4.3.1) to receive assistance and restricting assistance to speeds below 25 km/h. With the usual controllers, a 200 W maximum means much lower power over most of the operating range, so most Australian electric bikes probably exceeded the previous requirement. For those bikes that didn't, the change from "not more than" to "continuous" means motors are potentially a lot more powerful than a 50 W increase would imply. The continuous motor rating power is only loosely related to instantaneous power as shown in figure 4.
Figure 4: The rated power is at the intersection of the rated speed and rated torque lines. The position of the sloping line is determined by the rated voltage. The rated values are nominated rather than physical properties of the motor.
The continuous motor rating is a value assigned by the manufacturer at which the motor is guaranteed not to exceed temperature specifications as defined in IEC 60034-1 clause 8.10 - Limits of temperature and of temperature rise.  As an example, Bosch mid drive motors, rated at 250 W, have input power measured in figure 5, above 600 W for considerable periods while climbing a 5.5% grade pedalling at speeds around 23 km/h prompting reviewers to conclude the "Bosch mid drive feels as zippy and fast as 750-watt hub motor bikes."

Figure 5: Bosch mid drive input power while climbing a 5.5% grade pedalling at speeds around 23 km/h. Output power is probably about 75% of input power.  
Fast cyclists exceed speeds of 25 km/h, so incapable riders seeking to keep up will need assist at speeds above 25 km/h. EN 15194:2009 clause 4.2.6.2.2 c) specifies that the maximum speed test should be conducted at 1.25 times the rated speed, therefore some assist can actually be provided up to 31 km/h and still comply. This is above the speeds the average rider can maintain on flat ground but far short of the 41.6 km/h Chris Horner maintained over 172 km in the sample ride. Bosch overcome this limitation by also selling a "Drive Unit 45" version which lifts the rated cut off speed to 45 km/h.

Motor Selection

The Cute Q-85SX/GBK-85F, detailed in this drawing was suggested by Albert van Dalen. It is nominally 1.6 kg but was tested as 1.84 kg including electrical cable. He doesn't consider a lighter, nominally 1.2 kg motor in the Cute drawing, which may not be purchasable, and he chose the Cute over the Tongxin/Keyde which is nominally 200 gm lighter at 1.4 kg as the Cute was more easily acquired3. Accepting his motor recommendation, Albert's motor testing data can be used to model e-bike scenarios.

Motor Model

Albert conducted a carefully documented motor investigation and dynamometer test from which he constructed a motor  model. The dynamometer data, in figure 6, shows evidence of saturation beyond torques of 20 Nm, corresponding to a motor current of 12.9 amps, so a model is only valid for torques <20 Nm. Saturation could be avoided with more iron, but space is limited so that would necessitate less copper, increasing electrical resistance and reducing motor efficiency at torques <20 Nm. To avoid rapidly increasing inefficiency and overheating, this motor should be operated at currents less than 12.9 amps, though higher currents are sometimes used. This matches the Ku63 controller which limits current to 12 to 12.85 amps.

Figure 6: Dynamometer test data

Albert measured motor winding resistance as  ≈ 0.307 Ω (stated as  but intended as Ω) but elsewhere he calculated R = 0.77 Ω which is a substantial difference.  He accounts for the difference as gearbox friction and uses the measured value in his model, however the relationship:- Vo = (I * R) + (ω * Ke) which is expressed in Albert's notation as U = (I * R) + (ω * k) is independent of gearbox friction losses. Rearranging to k = (U - I * R)/ω, the motor constant (k) can then be plotted against rotational speed (ω) of the wheel using the dynamometer test data as shown in Figure 7.

Figure 7: Motor constant k versus ω with R = 0.307 Ω. Slope should be zero.

Adjusting to R = 0.75 so that the slope of a linear estimate of k = 0 gives the result in Figure 8.

Figure 8: Motor constant k versus ω with R = 0.754 Ω. Mean value of k = 1.55.  Note: The y axis scale is different to figure 7.  
The inconsistency of the estimated resistance with the measured resistance is a mystery which would be good to resolve. The estimated resistance is used for the motor model.

Torque is measured after the gearbox and is reduced by friction losses as shown in figure 9.

Figure 9: Different types of friction losses sum to the total friction loss. Friction at velocities near zero are ignored as  very low speed behaviour is not modelled.  
The losses in torque due to viscous and coulomb friction in the gearbox and motor can be modelled as:-
T = (Ts - Cv * ωs - Cc* Ts) * GR
where:-
T = wheel torque (Nm)
Ts = torque before the gearbox (Nm)
ωs = motor speed before gear box (rad/sec)
Cv = viscous friction coefficient
Cc = coulomb friction coefficient
GR = gearbox gear ratio

Combining with the motor equation:-
Ts = ks * i
where ks = motor constant before gear box (Nm/A)
and:-
k = GR * ks
where k = motor constant at the wheel (Nm/A)
and rearranging gives:-
k = (T + Cv  * ω) / (i *  (1 - Cc))


Figure 10: Motor constant k versus motor speed ω with R = 0.754 Ω. Mean value of k = 1.55.

Values for Cv and Cc can be found numerically to best match k to the previously determined value while minimising the slope of a linear estimate of k as shown in figure 10.
Resulting in:-
Cv = 0.033
Cc = 0 which means Cc can be ignored in the motor model.

The patterns evident in figure 10 suggest the model is not fully representative of the motors behaviour but the resultant errors are acceptable and being determined from large numbers of independent measurements should be considerably less than the estimated 5% error for individual measurements.

The parameters R = 0.754, k = 1.55 and Cv = 0.033 can be used to construct the motor model which can then be combined with the previous bike model and used for simulations of electric bike scenarios in a future post.

References

  1. Renesas Application Note: 180 Degree Sinusoidal Motor Control  Based on this document; pg 3; " As many brushless motors have sinusoidal BEMF ..., it is possible to match these motors with a sinusoidal driving voltage."
  2. Johan Astrom;  Investigation of Issues Related to Electrical Efficiency Improvements of Pump and Fan Drives in Buildings; PhD Thesis; Department of Energy and Environment, Chalmers University Of Technology, G¨oteborg, Sweden 2011; Figure 6.23 pg 97;  The graph shows marginal improvement, about 3% maximum in part of the efficiency/load curve with an optimal control scheme over standard BLDC motor control for a 375W motor. 
  3. Personal correspondence.

Sunday, December 16, 2012

What Would It Take To Cycle Fast When You Can't?

Working with pro cyclists has inspired me to cycle more. However, I'd like it to be easier when I'm weary or climbing a hill and I'd like to keep up with the guy in front. Less body weight and increased aerobic fitness would help but no amount of training could get me up with the young guys. I don't want a motorbike but some stealthy assistance would be nice.

I've trialled electric bikes from Switched On Cycles for a couple of weeks and the experience is good but not ideal.

Electric Bike BLDC Hub Motor
Figure 1 - A bike trialled with a rear hub motor. A front wheel drive bicycle was also trialled that had a Bafang, nominally 250 watt motor powered from a 36 volt battery.
The bikes work well for a commuter seeking to journey with minimal effort but are non optimal for my ambitions. The motor was quiet but audible, I'd like quieter if possible. I tried using the throttle modestly but its hard to sense the level of assist and power at these levels is as addictive as heroin. A little bit feels good so you want more and taking it away causes pain. On the flat, the motor can get the bike along at a reasonable speed without pedalling so the temptation to slack is as hard to resist as a good snack. Exerting the willpower to ride hard causes the power to fade as the speed increases so that I still can't catch the guy in front. Pedalling up a modest hill though is much easier and climbing Black Mountain at average grades of 9% I can pass the young guys. Surprisingly though, I have to pedal hard and at the top I notice the motor is sizzling.

I want a bike as close to a normal road bike as possible, that is silent, has a motor battery combination that is as light and unobtrusive as possible and doesn't run out of puff until I complete the ride. It's also apparent that whatever well planned strategies I might have for power management I behave like a junkie. My addiction, once I'm gasping for breath and the heart is pounding will cause me to abandon good intentions and seek immediate relief if all it requires is to twist the throttle.

Estimating Power Needs

Using a standard bicycle power model for a flat road and with my parameters estimated as:-
Rolling resistance Cr 0.004
Air density ρ  1.225 [kg/m²]
Drag coefficient  1
Reference area 0.5[m²]
Transmission eff. 97 [%]
gives me the result in Figure 2.

Figure 2 - My power vs speed model for a flat road and a windless day.
Above 15 km/h it can be seen most power (Pdrag) is consumed pushing air out of the way and air drag increases with velocity cubed so that it quickly becomes dominant. A person weighing 82 kg produces about 95 watts to walk at a brisk 4.8 km/h and 57 watts at a more leisurely 3.2 km/h, according to table 1 of "The Energy Cost of Walking" after applying the suggested thermal efficiency of 30%. From Figure 2 this will get a bike along at 18 km/h on level ground.

From Table 1 I can average 24 km/h on a good day over a fairly flat 5.2 km section of a 36 km ride around Lake Burley Griffin which, from Figure 2 equates to about 120 watts. The estimate of reference area and drag coefficient is crude so it is probably +/- 15 watts  of the true value but its close enough for some comparisons.

Rank
Date Speed (km/h)
1 Nov 25, 2012 25.1
2 Dec 2, 2012 24.8
3 Nov 29, 2012 23.9
4 Dec 16, 2012 23.8
5 Nov 18, 2012 23.5
6 Nov 24, 2012 23.2
7 Nov 30, 2012 23
8 Dec 3, 2012 22.9
9 Nov 26, 2012 22.3
10 Nov 23, 2012 22.3
11 Nov 14, 2012 21.8
12 Nov 13, 2012 19.6
Table 1 - Speeds over the same fairly flat section. 
The fastest rides might have benefited from a favourable breeze.

With a 500 watt motor the bike could get to 41 km/h but adding in my best average effort, would get a barely noticeable 3 km/h more. I doubt I could raise the motivation to do it. So at 500 watts I would already be riding a motorbike, albeit a dissatisfying one. It requires something like the Stealth Bomber at 4.5 kW to satisfy the power craving and by then the pedals are just for decoration. As for our reaction to artificial humans, it seems the level of satisfaction from extra power suffers an uncanny valley.

Chris Horner's 172 km ride in stage 4 of the 2011 Tour De France has been published and analysed.

Figure 3 - Chris Horner's ride data from stage 4 of the 2011 Tour de France
He averaged 215 watts for the whole stage, so a mere 95 watts of assist could put me in the peloton with Chris. For the final 25 km he managed 318 watts so I'd need 200 watts of assist to stick with him there but its still not much. He also managed 502 watts for 2 minutes and peaked at 710 watts. I could up the power a bit for 2 minutes too but I'd need some significant extra assist to match Chris and a 10 second sprint finish, which Chris didn't do in stage 4, would crush me. Chris also used his power more efficiently than the model for me predicts, averaging 41.6 km/h. He does this by riding most of the race on the wheel of other riders to reduce air drag and may (or may not) have had a tailwind. He also has a small cross sectional area maintained by a good pose and the small volume needed for his weight of just 64 kg, including the bike. Low weight  helps hugely on the hills as well.

I'm not aiming to match Chris in all circumstances but an extra 100 - 150 watts peaking at 250 - 350 watts of silent, light weight electric power, strategically provided by an algorithm I can't abuse would put me in the ball park. Much more than that would put me well ahead of the Tour de France field but leave me dissatisfied in the uncanny valley on a gutless motorbike.

Update

I sought feedback on this article at Endless-Sphere and there was a substantial debate, which I've summarised here.

 NeilP spoke for many:-
NeilP wrote:
Ken Taylor wrote:Do experienced ebike riders always get more satisfaction from more power?

:P YES YES YES YES YES!!! :D

and some like:-
maydaverave wrote:I have a low power 1000 watt bike. Its a great commuter for my small town and as time goes by I find myself going slower on it.

had a different definition of low power than I'd intended.

Kraeuterbutter at viewtopic.php?f=28&t=37785#p587951 is somewhat sceptical of the power requirements of Endless Sphere aficionados. 

However, there was some with plenty of experience of high power bikes who saw merit in low power bikes which I'd define as not more than 2-3 times more power than pedalling. For example:-

chvidgov.bc.ca wrote:I've experienced this when I recently put a "Cute" motor on a nice light aluminum framed roadbike.... I've been very happy with the very bikelike experience


Jeremy Harris wrote:I started out with a fair bit of power, but find that the ebike I like best, and ride most, is the light one with the low power motor. The reasons aren't that straightforward, I think. 


melodious wrote:....That article does have merit. A bike w/motor takes the physicality of the experience away. I'm really hesitant to taint my last true bike into a motorized vehicle. :|


Some commented on the psychology of power:- 

dogman wrote:A great deal depends on the goals of your ride. As goals change, the mental attitude changes.


rocwandrer having never ridden an e-bike felt unqualified to add to the discussion but pointed out that:-

rocwandrer wrote:The vast majority of my riding time is purely recreational, with the destination being the departure point.


which is probably pretty common and my favourite version of cycling. After presenting the reasons he claims:-

rocwandrer wrote:If the benefit from adding pedal power does not FEEL proportionate to the effort, it is much harder to put in that effort....That all matches with Ken's hypothesis that if there is enough power on tap with the electric assist to make the human contribution feel less critical, or to make the return for extra effort feel too small, it is will psychologically difficult to even acknowledge that there is more in reserve in the human power side's controller.

Thursday, November 1, 2012

Innovative Value Transfer Systems For Government

There is potential to improve government transfer payments through innovative payment systems that make it easier to issue funds, spend the benefit and automatically capture the accounting information. Such a system could be used for government transfer payments for a wide variety of purposes.
Advantages include:-
  • Recipients would use a common method of receiving and spending many different payment types.
  • A recipient would be immediately aware of having received the benefit and the value of the benefit.
  • A controlled market could be created to capture the advantages of market economies while restricting products and services to the types intended.
  • The funds associated with the benefit are not spent until the service provider claims from the government.
  • Transfer payments not consumed by the recipient will automatically evaporate. 

Government Transfer Payments

A transfer payment is made without any exchange of goods or services. Examples of transfer payments include welfare (financial aid), social security and government making subsidies for certain businesses. 

The Henry Tax Review [1]  considered transfer payments and concluded "A coordinated approach should extend to the consideration of housing assistance, access to aged care and transfers that are tied to expenditure on other goods and services. A coordinated approach would support greater equity between transfer recipients, reduce the inherent disincentives to work created by taxes and transfers and underpin a better client experience of the tax and transfer system." The  tax review describes several classes of transfer payments:-
  • family-related payments 
  • child care, housing assistance
  • transfers tied to goods and services
  • aged care
Transfer payments are intended to achieve a social purpose. Those tied most narrowly are where "governments also provide other transfers in the form of concessions or payments that are linked to the purchase, or supply, of a particular good or service"[1] but others including childcare,  housing assistance and some aged care services are also intended for quite narrow purposes. Governments currently employ a variety of methods to ensure payments are directed towards the desired purpose.

Innovative Value Transfer Systems

Innovative value transfer systems have been slow to develop in the information age and many have failed. "While electronic money has been an interesting problem for cryptography .., to date, the use of e-money has been relatively low-scale."  Probably the most widely used  information age payment system, Paypal is grafted on to previously existing card payment networks and provides barely distinguishable services.

Strategic Review of Innovation in the Payments System - RBA

The Australian Reserve Bank has an interest in fostering innovation in Australian payment systems and government transfer payments should be part of that innovation.  The recently completed Strategic Review of Innovation in the Payments System had "the objective of identifying areas in which innovation in the Australian payments system could be fostered through more effective cooperation between stakeholders and regulators."[2]

The review sees "the potential to unlock significant future innovation, resulting in ongoing improvements to the efficiency of the payments system.... the Board intends to be more proactive in setting out strategic objectives for the payments system, that is, its expectations for the services that the payments system should be able to offer in the future." 
The review considers the key attributes of payment systems to be:-
  • Timeliness
  • Accessibility
  • Ease of use
  • Ease of integration with other processes
  • Safety and reliability
As government transfer payments represent an important component of the payment system there is an opportunity to influence the direction of innovation in partnership with commercial partners.

Fungible Value

In standard payment systems value is fungible, meaning it is transferable for any purpose, but many government transfer payments are intended for a particular purpose and it is in this area that innovative payment systems can contribute. An innovative payment system could be used to create a closed economy where a payment can only be made to approved suppliers for intended purposes. Within that closed economy normal trading can occur. This is ideal for government transfers in the form of concessions or payments that are intended for the purchase, or supply, of a particular class of good or service e.g. laptops for school aged children.

An Innovative Example - Bitcoin

Bitcoin is a new payment system that is often though of as libertarian but it has characteristics that could be utilised for government transfer payments. Variants of Bitcoin, known as alt-coins could be used for transfer payments or aspects copied in alternative value transfer mechanisms. Most importantly, Bitcoin has been shown to work, is in active use and has a suite of tools and services under development. A level of granularity in transaction data and payment flows down to individual items or services is achievable and separate alt-coin currencies can be generated for each class of transfer payment. It is at least useful for exploring what is possible and the desirable characteristics of value transfer systems.

Characteristics Of Bitcoin

Simple To Use

The underlying mechanism is invisible to users making it simple to understand and use. It usually requires an internet connection and payment device which can be a PC application,  a web browser app or smart phone app. However, paper based transactions are also possible.

A person is presented with a bill, can use their smart phone camera to read the bill and can authorise the transaction with a key press. In the future it is likely that, using OpenPay, a consumer will be able to spend bitcoins at any merchant that is able to accept Visa or Mastercard.

Preserves Privacy

Because transactions are broadcast to the entire network, they are inherently public. Privacy is maintained through anonymous account numbers.

Simple Accounting

Transaction data is captured as part of the transaction without requiring additional reporting. If the mapping is known, transactions can be traced from account numbers to individuals. In a government transfer system the government issuer would create that mapping.

Others

Bitcoin is an innovative payment system gaining traction but there are many others as described in the Electronic Money Wikipedia article and the RBA's Strategic Review[2] provides a model for real-time retail payment and settlement hubs which includes a list of desirable characteristics.

Current Mechanisms For Transfer Payments

Direct Payments

Most direct payments are not linked to the purchase, or supply, of a particular good or service and work well with current payment systems.

The BasicsCard

The BasicsCard is a stored value EFTPOS card provided by the Department of Human Services that allows purchases for authorised items from authorised merchants.
The merchant enforces the restriction to authorised items and the EFTPOS system can't create an audit trail to verify this restriction. It has attracted some controversy but Jenny Macklin, the Minister for Families, advises "We've had it now operating for a few years; we know that it's helpful. The individual stories are very positive." It's proven there is a desire for government transfer payments to be directed to particular areas but the BasicsCard is limited to the options provided by the existing EFTPOS system and is not suitable for many forms of transfer payment, for example Renewable Energy Certificates. Innovative value transfer technologies can extend the BasicsCard concept.

Tax Benefits

Some transfer payments are claimed through the tax return. This method is cumbersome, creates a delay between incurring the expense and claiming the benefit and puts a substantial administrative burden on claimants. An example is the Schoolkids Bonus formerly known as the Education Tax Refund. It is intended for expenses such as uniforms, books, school excursions, stationery and other costs like music lessons and sports registration fees. Previously, proof of expenditure was required by claimants but to reduce the administrative burden the requirement was removed so that the benefit is only notionally provided for the intended purpose. Innovative value transfer technologies could restore the original concept of directing the payment to the intended purpose and make the benefit available in an attractive form that can be spent rather than received as a refund.

Direct Provision of Goods and Services

Sometimes governments directly provide goods and services when a superior outcome could be achieved by a transfer payment combined with market mechanisms. An excellent example is the laptops for schools program. Some students never got a machine. The machines supplied required tendering and administrative processes that introduced massive delays. There was a transfer from parents to government of the burden of ensuring responsible use and the $1,000 per machine supplied by the federal government proved insufficient to cover the machine and program costs so that in extreme cases parents were asked to contribute more per machine than the cost of a similar machine from a retailer. Use of the existing supply chain with an innovative transfer payment solution would have achieved a better result.

Voucher Systems

Renewable Energy Certificates (RECs) are a tradeable voucher for encouraging investment in green energy initiatives. "Eligible renewable energy sources are entitled to create certificates based on the amount of electricity they produce or displace. These certificates can be created in the REC Registry and sold to buyers."
These vouchers are quite different to payment systems like the BasicsCard but to an innovative value transfer system RECs would appear as just another value type and be traded in the same way a beneficiary trades their laptops for schools benefit. The trading system would automatically perform the function of the REC registry.

References

1. Australia's Future Tax System Review; Chapter 9: The transfer system; Australian Government; May 2010.
2. Strategic Review of Innovation in the Payments System: Conclusions
June 2012; Reserve Bank of Australia