Control

From Trevipedia

This page will eventually discuss:

• motor controllers
• power stages
• control stages
• motor control algorithms
• interfacing to power and brake pedals
• interfacing to battery management system
• interfacing to instrumentation.

Motor controller

Possible motor controllers:

• Altrax make controllers for 72 V brushed DC motors, and provide some good overview material on control and system design matters.

• Curtis make a variety of controllers. The prototype Trev driven from Darwin to Adelaide used a Curtis 1231C series motor controller with an Advanced DC X91 4001 series wound brushed motor. This combination was too powerful, and did not allow enough control over acceleration at low speeds. The Curtis controllers are mainly for low-voltage systems.

• Kelly Controls make a variety of controllers for brushed and brushless motors.

• Semikron make integrated power modules suitable for driving brushless motors. UniSA is currently building a controller based on a Semikron SKAI 4001 GD06 1452L (air cooled, 450 V DC link, 245 A continuous). This power stage will deliver much more power than we need. A smaller, lighter controller would be better.

• Open Source Motor Controller Members of the Ecomodder community are cooperatively developing a 144 volt 500 amp controller. Estimated cost is around $150-250 unassembled

Driver controls

The driver controls are:

• power switch: Off / Accessories / On
• direction selector: Forwards / Off / Reverse
• accelerator pedal (5 kOhm resistor)
• brake pedal (5 kOhm resistor)
• left indicator (momentary push button on steering wheel)
• right indicator (momentary push button on steering wheel)
• horn (momentary push button on steering wheel)
• hazard lights switch
• position lights / dipped-beam / main-beam switch on dash
• windscreen cleaning controls

The power switch is wired directly to the 12 V battery. The remaining controls are wired to a driver controls box in the cab, which transmits commands to other parts of the car using a CAN bus.

Direction, accelerator pedal postion and brake pedal postion are polled every 100 ms. The driver control box calculates the required direction, maximum speed and maximum torque, and sends these to the motor controller on the CAN bus. (If the motor controller does not receive these values for, say, 200 ms then the maximum torque is set to zero.)

When the car is started, the maximum torque should be held at zero until the accelerator has been fully released and the direction selector is in the OFF position.

Other button and switch positions are transmitted only when they change.

The hazard lights must operate even when the power switch is off, so should be wired directly to the 12 V battery. Diodes (or something) will allow the indicator lamps to be operated by either the hazard circuit or from the lighting controller.