P15241: Autonomous People Mover - Remote Control
/public/Modifications/

Electrical_Modifications

Steering Photos
The electrical interface with the steering system consists of 12V power for the motor as well as a 5V input to the system’s internal controller. Control is provided by two differential inputs coming from the torque sensor that read the torque input from the driver. This input torque is then scaled by the Wicked system and applied to the steering column. To interface with the system the torque sensor lines were connected to relays along with input lines from the designed control system. When power is applied to the relays the output connected to the Wicked system switches from the torque sensor to the signal lines from the control system.
Braking Photos
The braking system of the golf cart also had to be modified, however not as significantly as the steering. To implement remote braking an actuator was used to pull a steel cable that was connected to the brake petal. Due to the size of the actuator it required a pulley to make a 90° turn before connecting to the brake petal. The actuator and the pulley were mounted to the golf cart frame.

This method allows for the passenger in the driver’s seat to still be able to hit the brake in an emergency situation. For feedback the internal potentiometer of the actuator was used as well as a magnetic field sensor.

The braking system is controlled using a Sabertooth R/C Regenerative Duel Channel Motor Controller. This system requires a 12V input as well as a 1ms to 2ms-pulse width input signal provided by the designed control system. The potentiometer is used to control the position of the actuator and the magnetic sensor is used to sense if the passenger applies the brake so the golf cart can be stopped. To control the acceleration, the input to the controller of the golf cart was switched from the throttle potentiometer to an ADC from the controller.

In order to prevent a condition where the power and the ground to the potentiometer were disconnected, a dummy 5kΩ resistor was used to emulate the throttle potentiometer. Without this the golf cart controller was found to experience a fault.

Dashboard Photos
The modified dashboard included five LED status lights, three green for the accelerator, steering, and braking systems, one green for the readiness of the overall system, and a one red for check engine. The large red button is the emergency stop button and the LCD is used to show the current speed, position, and time. The large red LED is a status light provided by the wicked system. Additionally the rocker switch with an LED is the autonomous/manual mode switch and the rocker switch next to the keyhole is the FWD and REV switch. To control all of the golf cart systems, three Arduino Dues are being used; one for the braking/accelerator, one for the steering, and the third for the dashboard and overall control. A board was created using Eagle PCB design software for general connections and support circuitry. The throttle and braking Arduino uses both available ADCs to output the accelerator control signal. The output of the Arduino ADCs are bound between .55V and 2.75V.