DC Motor Control

Many of the EFI Technology ECU products are capable of controlling a DC motor. The most common use for this type of output is for Drive by Wire throttle systems. The sensor on the drivers pedal provides the command signal to the ECU which in turn controls the engine throttle mechanically by driving the DC motor. A second sensor on the engine or motor itself provides feedback information to the ECU regarding the actual position.

Another common use of the DC motor output is for variable geometry inlet systems. The user can program a 3D map of the target position against two axes such as engine rpm and throttle. An additional sensor on the actual inlet position provides the feedback information to the ECU for the PID control loop.

DC Motor Constants

DC Motor Configuration - Enables the different options available for the DC Motor control.
Motor Frequency - Sets the DC motor control frequency. Typical values are 1 to 3 KHz depending on the motor type you are using.
Base Duty - Sets the base duty cycle for the PID loop. Typically set at 50% unless the motor requires bias.
Proportional Gain - Proportional gain constant. (see notes)
Integral Gain - Integral gain constant. (see notes)
Integral Timer - Integral timer constant. (see notes)
Derivative Gain - Derivative gain constant. (see notes)
Integral Band - Sets the operating window before the integral control of the PID loop becomes active.

Tuning

Start the Editor with the ECU connected and make sure that the correct map is loaded.
Open the DC Motor function group and constants window.
Enter the required target values at each of the rpm and throttle sites.
If you have selected drive by wire mode under the configuration constants the target value is the current value of the pedal position sensor. Be sure to calibrate this sensor before tuning your system.
Press the pedal and observe the movement of the throttle driven by the DC motor.
Adjust the Gain settings to obtain the best response of the DC motor without inducing oscillation.
Increasing the gain will speed up the overall response of the DC Motor control. Using an excessive amount of gain may lead to overshoot and can induce oscillation. A general rule is to increment the proportional gain by a quarter of the previous value until the output becomes unstable and then back down the gain a small amount.

Safety Controls

The safety controls are designed to detect an error in the drive by wire throttle system. If the engine throttle position fails to match the demand pedal by more than 7.5 degs in a 0.5 sec time period the motor is automatically disabled. To assist with initial tuning the safety controls can be disabled by checking the option under dc motor constants but it is recommended to leave active during normal operation.

Note: The safety control feature is only available when using the ECU internal DC motor driver. The optional high output external motor driver has no input to provide this function.

Notes

Please refer to the help file for further information on tuning PID controls.

Winning Edge Electronics