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:
- Neutral glide - at low speeds, the transaxel can go into neutral to 'coast' and flip
back into drive when either the accellerator or brake are used.
- Pulse and glide - under cruise control, pulsing "ACC" increases the speed by 1 MPH and pulsing
"SET" decreases the speed by 1 MPH. A small computer can use the current speed and motive energy
demand to pulse "ACC" and "SET" to achieve pulse and glide driving.
- Topology driving - using a magnetic compass and distance readings, a small computer can "learn"
the topology of several commute routes.
Upon recognition of an earlier, learned route, the computer can schedule the 'pulse' to optimize
Prius Classic Control Laws
On August 29, 2001, Jeff Muller posted some of the
earliest CAN databus
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:
- Below 40 MPH - the ICE turns off when not needed or generates power for the
- Between 40-47 MPH - the ICE idles at 1,000 RPM and may or may not generate usable
amounts of traction battery energy.
- Between 47-50 MPH - the ICE begins generating significant amounts of traction
- Above 50 MPH - the ICE pretty much generates motive power with little idle or MG1
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
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.
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:
- MG2 phase and speed
- MG1 phase and speed
- Park/Neutral "D" and "N"
- Accellerator position sensors VPA1 and VPA2
- Stop light switch
- Cruise control switch
- MG1 and MG2 lead monitors (external to HVC-ECU signals)
The primary controls are tri-stated, probably via mechanical relays:
- Cruise control switch
- Park/Neutral "D", "N" and VSFT/SFT/GSFT
To support both performance monitoring and topology driving, there will be a need
for non-volital memory and some form of uplink.
The angle of each motor is defined by the relationship between a reference signal and a sine and cosine
The expected reference signal is assumed to be a 10 kHz RMS signal
as described in the
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
The tricky part is the reference voltage will be monitored, not generated by the phase angle