Actuation Control

Steering Motor and Driver

24a utilizes an additional steering motor in part of the Autonomous Steering System. The selected motor, Maxon EC Flat, is paired with the EPOS series motor controller to enable the control of the system. Steering control actions are sent via CAN from the onboard computer to AIM. PID control loop processes these commands against feedback from the steering angle sensor, translating the output into appropriate ADC values for the motor controller to achieve the target steering angle position. The steering angle sensor, installed on 24a’s steering rack, is calibrated by attaching an IMU device onto the front wheels to record angular deviation from the center position, alongside corresponding steering angle sensor ADC values, creating a mapping for accurate feedback.

Driverless System Brake (DSB)

FSAE DT.3.1 requires driverless vehicles to be equipped with a driverless system brake for use during the driverless missions. 24a utilizes the AMK hub motor’s regenerative braking capabilities to meet deceleration targets and is not equipped with an additional actuator.

Emergency Brake Actuator and Pressure Sensors

24a is equipped with two pneumatic brake pressure sensors that provide an accurate reading of the EBS pneumatic line pressures. The output of the sensors are in the analog range of 0.5 ^ 4.5V, which are read through AIM along with the pre-existing hydraulic brake pressure sensors to be used for safety checks in various states.

  • Driverless State-up Safety Check (EBS Pulse): Upon entering into a driverless Ready-to-Drive state, AIM briefly enters an error state in order to open the safety circuit, triggering the EBS. At this instance, AIM reads the pressurized EBS brake line pressure and the hydraulic brake line pressure through these sensors and checks if it passes a certain threshold required to fully lock the brakes, ensuring that the car is able to fully stop safely when necessary.

  • Continuous EBS Tank Pressure Monitoring: During the DS Driving state, AIM continuously checks for any pressure loss below the threshold value in the EBS pneumatic tank, to ensure a safe EBS functionality. In the case of the pressure drop, the EBS relay on AIM is triggered to open the safety circuit and activate the EBS. The threshold is determined to ensure at least a single safe activation before it reaches depletion.

Onboard Computer and Perception Sensors

The onboard computer is the “brain” of the driverless system, processing sensor data, running perception, path planning, and control algorithms. The Cincoze GM-1000 was used as our onboard computer . Our key requirements included:

  • Power: Ability to take in 24VDC, with sufficient power delivery for all connected peripherals.

  • Cooling: Adequate cooling solutions were essential given the high processing demands and potential for elevated temperatures in a race car environment.

  • Interfaces: Ample I/O ports (USB, Ethernet, CAN) for connecting various sensors and connections to the rest of the vehicle.

  • Processing Power: Sufficient CPU and GPU power to handle the driverless software pipeline’s computational requirements, real-time perception and control.

In addition to the onboard computer, 24a is equipped with a Hesai AT128 LiDAR and two ZED stereo cameras for perception sensing. The GM-1000 and the LiDAR are directly powered from LVMS while the stereo cameras are powered from the onboard computer.