Version 00.01, Dec. 12, 2005 - Added implementation notes, still not spelling checked.


A drive-by-wire vehicle, the Prius Classic engine and motor-generators are computer operated. This offers some unique opportunities to automate these high mileage techniques:

Prius Classic Control Laws

On August 29, 2001, Jeff Muller posted some of the earliest CAN databus observations, Muller010825c.xls. By plotting internal combustion engine (ICE) and the sign of MG1 spin, we get a plot showing the control laws in action:

When the MG1 rotates in a negitive direction, it is either generating electricity from the ICE or keeping the ICE in 'neutral'. A positive MG1 rotation means MG1 is transmitting torque from the ICE to the wheels. Jeff's data goes a long way to explain earlier MPH vs MPG performance observations:

Neutral Glide

A small controller will monitor the speed, accellerator position and brake and the gear selector for "D". When going slow enough, below cruise control managed speed, with the accellerator and brake off and gear in "D", it will change the signals from the gear selector from "D" to "N" including the secondary resistor network value. Upon application of either the accellerator or brake, it will revert to the existing "D" setting. Changing the gear to anything else will also turn-off the gear setting override.

Pulse and Glide Cruise Control

A small controller will monitor the speed, accellerator position and brake, ICE and MG2 energy state, and the cruise control input settings. With the cruise control "ON", a single "SET" will be ignored. However, a double "SET" within one second will enable the pulse and glide mode using the current speed as the upper limit.

It will monitor the energy flow of MG2 and the ICE. If the energy flow is essentially none, nothing will happen. If the energy flow from MG2 is regenerative and the speed is less than the original "SET" speed, it will enter "ACC" and let the vehicle achieve the new expected speed before re-evaluating another "ACC" increment. It will stop when the "ACC" is back to the original double "SET" speed.

Should the energy flow of MG2 and or the ICE be for traction, it will enter a "SET" to reduce the speed by 1 MPH. When the new speed reduction is achieved, it will continue as long as traction energy is needed until reaching a minimum speed, typically 5 mph below the original double "SET" speed. If there remains an need for more traction energy, it will enter as many "ACC" as are needed to bring the vehicle back to the original double "SET" speed. Once the target speed is reached, it will revert to energy monitor mode and wait for the double "SET" speed to be achieved.

Pressing the brake or turning off the cruise control will disable the pulse and glide until another double "SET" is entered. Accellerating above the double "SET" speed will suspend pulse and glide until the double "SET" speed returns and then pulse and glide resumes.

Topology Driving

A variation of pulse and glide, a small processor will use a magnetic compass and distance measurements to identify frequently used routes. As each route is "remembered," the energy profile and braking patterns will be monitored and recorded to identify where energy is needed and areas where gliding is optimal. Furthermore, it will remember the double "SET" points as target speed limits. The system 'learns' the commuting routes including the speed limits and location of intersections, probability of stops and inclines. It does this with just historical, dead reconning navigation.

Having learned the commuting routes which invariably start with the vehicle "OFF" and at the last 'known' point, it monitors the initial commute. Once a route or selection of routes is recognized, it will wait for the double "SET" and then prompt the driver to "drive the topology." Hitting "OK" will let the topology map set the double "SET" speeds to maximize fuel economy.

Dropping out of pulse and glide idles topology driving except to monitor and pattern match the route to the list of commute routes. Putting the vehicle back in pulse and glide mode will again let it prompt for "topology driving."


The primary drivers are the sensors that monitor these signals:

The primary controls are tri-stated, probably via mechanical relays:

To support both performance monitoring and topology driving, there will be a need for non-volital memory and some form of uplink.

Singlsyn Resolver

The angle of each motor is defined by the relationship between a reference signal and a sine and cosine return signals. The expected reference signal is assumed to be a 10 kHz RMS signal as described in the Singlsyn specifications.

Although it may be possible to use high-speed A/D convertes and software to resolve the angle and rotation of each motor, a better design will use an AU6802N1 or equivalent part to handle decoding the phase angle and rotation speed. The tricky part is the reference voltage will be monitored, not generated by the phase angle resolver.