Motor & Controller

The motor used to turn the steering wheel is a Midwest Motion Product D22-376D-24V GP52-029. The motor is a planetary, reversible DC gearmotor that provides the torque and the speed fit to turn a standard steering wheel of a utility vehicle. Table 1 provides the specifications of the motor.

Table 1. Motor specifications

Mounted to the back of the motor is an EU optical encoder that produces 500 pulses per revolution. Figure 1 shows the motor with the encoder mounted.

Figure 1. Midwest Motion Product D22-376D-24V GP52-029 and EU optical encoder

The controller used to control the motor is a Roboteq MCD2460S brushed DC motor controller. The controller is capable of outputting 120A and driving a single brushed DC motor forward and reverse. Figure 2 contains the controller.

Figure 2. Motor/controller power connections

The controller also provides encoder inputs that allows open loop or close loop, position and speed motion control. Figure 5 shows the connections from the encoder to the encoder inputs of the controller.

Figure 4. Diagnostic LED status patterns

Figure 5. Encoder/controller connections

The controller is able to receive commands from a RC radio, analog joystick, or a PC via RS232 or USB. Roboteq provides a free PC utility, Roborun+, which provides a user-friendly graphical interface to control the motor speed or position. Using the Roborun+ technology, a user can also write scripts to control the motor using MicroBasic, a Basic-like computer language. Roboteq also provides users with the Roboteq Devices application programming interface (API), which tells how to communicate with the controller for reading parameters and sending motor commands. Figure 6 shows a screenshot of Roborun+.

Figure 6. Roborun+ Motor Control Utility

As shown in the figure above, Roborun+ allows the user to read and plot the values such as current, temperature, speed, and voltage. The utility also shows additional status of the motor. Using Roborun+, testing was done in lab, using a variable power supply, and in a standard utility vehicle. Table 2 shows the results of the testing.

Table 2. Testing results

Appendix C

Automated steering can have a big impact on the society. With this invention, on a bigger scale, it can lead to all cars being automatically driven or controlled by an outside source. One change I think about is a change in the cab or car service. With professionals driving or one big system controlling all driving, roads can become safer. Inventions like this can also ruin a good amount of jobs and careers involving driving. Another big concern is getting people to trust in an automated driving system. The dependency of these cars will be in question with other drivers still on the road; how will you adapt to something as unpredictable as a human being.

To fulfill the design requirements, it took us learning some mechanical engineering concepts. Before we could pick a motor, we had to find the torque needed to turn the steering wheel. We also had to think of how fast a person normally turns a steering wheel while driving. We had to use a torque wrench to measure the torque we will need and it took us driving the utility vehicles provided many times to see how fast we would normally turn the steering wheel. This information is incorporated in the motor we ended up deciding on.

-Donald Ragland

With .25” Faston tabs, the controller can be connected simply to the motor. Figure 3 shows the power connections between the controller and the motor.

The controller provides stall detection and selectable actions if current is outside of the user-selected range. Protection against overvoltage, undervoltage, and overheating is also provided by the controller. Using the diagnostic LED, the user can monitor the status of the controller. The flashing patterns for the diagnostic LED is shown in figure 4.

Figure 2. Roboteq MCD2460S brushed DC motor controller

Figure 3. Motor/controller power connections