Vehicle Speed Governor for Low-Speed Torque and Load Control
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Solution Overview
Problem
Direct-drive electric vehicles face inefficiencies at low speeds and challenges in calibrating vehicle speed due to varying transmission gear ratios, rear axle ratios, and tire sizes, necessitating precise control over motor output torque and vehicle speed management.
Innovation Solution
A vehicle speed control system comprising a motor, vehicle speed sensor, brake mechanism, and controller that adjusts output torque based on vehicle speed limits and brake mechanism states, using speed droop functions to manage vehicle speed and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a direct-drive electric vehicle operates at very low speeds and loads, then the vehicle can maneuver precisely in parking situations, but power efficiency deteriorates
Solution Approach 1:
The vehicle speed governor dynamically adjusts the vehicle speed limit based on brake mechanism state (released or applied) and load conditions. The controller continuously modifies the output torque command to the motor, transitioning between different operational modes to optimize both low-speed maneuverability and power efficiency. This dynamic adaptation allows the system to maintain precise control at low speeds while improving energy utilization.
2Device complexity
If the vehicle speed governor uses a fixed pre-set vehicle speed limit, then the control system is simple, but the system cannot adapt to varying load conditions and different directions of travel
Solution Approach 1:
The vehicle speed governor transitions from a static pre-set speed limit to a dynamic speed limit that adapts to varying conditions. The system adjusts the vehicle speed limit based on brake mechanism state (released or applied) and load conditions, enabling the control system to respond to different directions of travel and load variations while maintaining reasonable control complexity through algorithmic adjustments.
3Adaptability or versatility
If different transmission gear ratios, rear axle ratios, or tire sizes are used, then the vehicle can be configured for different performance requirements, but calibration of vehicle speed relative to motor speed becomes challenging
Solution Approach 1:
The vehicle speed governor system automatically adapts to different vehicle configurations (transmission gear ratios, rear axle ratios, tire sizes) through dynamic adjustment based on brake state and load conditions. Rather than requiring manual calibration for each configuration, the system self-adjusts the vehicle speed limit and output torque commands, eliminating complex calibration procedures while maintaining configuration flexibility.
Data Source
AI summary
A system for controlling a vehicle speed of a vehicle is described. The system comprises a motor, a vehicle speed sensor, a vehicle speed governor, and a controller. The motor is configured to provide an output torque for driving the vehicle. The vehicle speed sensor provides a vehicle speed signal corresponding to the vehicle speed. The vehicle speed governor has a vehicle speed limit for the vehicle, where the vehicle speed governor adjusts the vehicle speed limit according to a desired direction of travel of the vehicle and a load corresponding to the motor. The desired direction of travel is selectable by an operator of the vehicle. The controller is configured to adjust the output torque of the motor according to the vehicle speed limit and the vehicle speed signal.