This is an informal request for custom vehicle builders and modification shops to modify a vehicle for us. The vehicle will be entered in the DARPA Grand Challenge competition - 200 miles on and off road, no driver. We're doing the computer and sensor parts. What we want from the car shop are the basics needed to control a vehicle with a computer - steering, brakes, throttle, and transmission. We are soliciting quotes for this work.

Vehicle selection

It's going to be an offroad truck, or something close to it. We want to start from a current-model truck and add some basic offroad modifications. These will include

• Full skid-plate coverage
• Puncture-resistant offroad tires
• Modest off-the-shelf suspension improvements.
• (Possibly) a differential locker.
  

Suggestions, and bids, in this area are appreciated.

In general, our goal is to have the vehicle finish the race. Speed is secondary. We do not envision exceeding 45MPH on-road, and off-road speeds will be much lower.

Sensors and computers

We will be adding a modified front brush guard, a modified rear bumper, and a cab-top unit mounted on a roll cage. Each of these will mount various sensors. Those units are not part of this job.

We will need to mount a dust and splash resistant electrical cabinet somewhere on the vehicle, probably within the cab behind the passenger seat. Dimensions to follow.

Steering

We need to control steering from a computer. The required performance is modest. We will issue steering updates at approximately a 15Hz rate. A lock to lock time of 2-4 seconds is adequate. We need to be able to read back actual steering position from the computer interface.

The steering actuator must be able to survive off-road operation, including poor driving. Anything that doesn't damage the vehicle's own steering gear should not damage the steering actuator system.

Ideally, the steering actuator should be unobtrusive from the driver's seat, and not interfere with manual driving. We will consider compromising on that if necessary.

Braking

Within our control system, we will command deceleration and acceleration in gravities, and close a servoloop with an accelerometers to achieve this. This is to stay within the circle (ellipse, actually) of accelerations for which the vehicle will not usually slip. (If we do detect slip, we'll make the circle smaller, which will moderate the control inputs.) We have enough sensors (rate gyros and accelerometers) to adjust these limits for hills.

So all we need is to be able to command pedal force. We need to read back pedal force, and also need to obtain any information the ABS system can provide to us. The minimum info is "ABS active". This will make the allowed acceleration circle smaller, which will cause our steering control system to straighten the steering if at all possible. (Yes, this is dumb by racing standards, but it's at least not totally naive.) If we can get more information back from the ABS system (it might be an advanced one, like GM StabilTrak), that's helpful.

We also need a "panic stop mode", which applies and holds maximum braking. This is triggered by the emergency stop system. Brakes must remain applied with power off and the engine stopped.

Throttle

In this area, we solicit your advice. Given the variations in modern engine control units, this may either be a purely electrical interface to the engine control computer or a physical actuator.

The throttle control system should contain an RPM limiter, with two manually-selectable settings. One setting, for testing in small spaces like parking lots, should limit speed to about 5MPH. The other, for operation in open areas, should limit speed to about 50MPH.

Transmission

We will be using an automatic transmission. We need to be able to control it only at the level a driver ordinarily would; we don't need to get into the transmission innards or modify what the transmission program is doing. We will probably only need Park, Low, Drive, and Reverse. If the vehicle has a 4WD transfer case, hubs, or lockers, we'll also need to control them.

As above, we need to read back the position of anything we can set. We also need to read back both engine RPM and vehicle speed as seen at the driveshaft. (We may be able to get those from the OBD port.)

Starting

We need to be able to start and stop the engine under computer control. We'll have to stop it for emergency stops, and we have to restart remotely afterwards.

Emergency stop

An emergency stop system is required. Both manual emergency stop buttons and a radio link will be provided. The emergency stop radio link will use an Omnex T110 (transmitter) / R150 (receiver). Radio emergency stop should force throttle to idle and a brake application, and report an emergency stop to the control system. Software will then wait until the vehicle has stopped, shift to Park, and stop the engine. Because radio emergency stop can be triggered by loss of signal when the chase vehicle gets out of range, it can't be too drastic. In particular, we don't want to kill ABS and steering control just because we're out of range. We will have to restart, remotely, after a radio emergency stop.

Manual emergency stop will be a series of normally closed industrial emergency stop buttons, plus a connection through a standard marine onboard fire extinguisher (a sprinkler head on a CO2 bottle). Manual emergency stop does the same things as above, plus it kills the engine. So if you have to approach the vehicle when it's in trouble, banging on any stop button stops everything.

The radio control unit has several extra outputs besides the emergency stop line. We will need to read those from the computer interface.

Computer interface

We want digital signals, but are flexible on the interface. CANbus, J1939, USB, or RS-232 are all acceptable.

Delivery

We have a new vehicle delivered to you, and you return it to us with the indicated modifications.