Electric Vehicle Motor Torque Control in Downhill Mode
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Solution Overview
Problem
Conventional electric vehicles face challenges in controlling output torque in downhill mode, leading to potentially excessive vehicle speed and safety issues due to inadequate braking torque, especially when the motor's torque control is based solely on the accelerator-pedal travel value without considering the vehicle's tilt angle and speed.
Innovation Solution
A method and apparatus that detect the vehicle's tilt angle, current speed, and accelerator-pedal travel value to calculate a downhill slip torque and adjust the output torque of the motor, incorporating a given vehicle speed delimitative value to prevent excessive speed, allowing for both forward and reverse torque output without pedal intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the motor controller calculates output torque based solely on accelerator-pedal travel value and maximum output torque, then the control system is simple, but the vehicle speed becomes uncontrollable in downhill mode due to inadequate braking torque
Solution Approach 1:
The control system performs preliminary detection of downhill mode through tilt angle sensing before torque calculation. By identifying downhill conditions in advance and adjusting torque calculation accordingly, the system prevents excessive speed accumulation rather than reacting after the problem occurs.
Solution Approach 2:
The system incorporates feedback from tilt angle sensors and speed sensors to continuously monitor vehicle conditions. The motor controller uses this feedback to dynamically adjust torque output, creating a closed-loop control system that maintains reliable speed control under varying downhill conditions.
2Speed
If the motor increases output torque with increasing vehicle speed in downhill mode, then the motor can maintain required speed, but the vehicle speed becomes excessively high and uncontrollable
Solution Approach 1:
The torque calculation dynamically adapts to downhill conditions by incorporating tilt angle and speed as variable parameters. The system transitions from static torque control to dynamic torque control that automatically adjusts based on real-time vehicle state, preventing excessive speed while maintaining controllability.
Solution Approach 2:
The system changes the control parameters from simple accelerator-pedal travel value to a composite calculation including tilt angle, vehicle speed, and maximum output torque. This parameter transformation enables the motor to generate appropriate reverse braking torque in downhill mode, maintaining vehicle controllability.
3Ease of manufacture
If the motor friction is used for braking in downhill mode, then no additional braking system is needed, but the friction is inadequate to prevent excessive vehicle speed
Solution Approach 1:
The motor serves dual functions: propulsion during acceleration and braking during downhill descent. By controlling the motor to generate reverse torque, the system uses the motor itself as the braking device, eliminating the need for separate mechanical braking systems while providing sufficient braking force.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively controls vehicle speed in downhill mode by calculating and outputting the appropriate torque, ensuring safety and maneuverability by preventing excessive speed and enhancing comfort by stabilizing low-speed increases.
Implementation Method 1
the motor controller may calculate the output torque of the motor according to the equation T = T 2 × Gain, and control the motor to drive the wheels of the vehicle by using the torque T
Implementation Method 2
When its speed is too high, the friction of motor is inadequate to form the reverse brake
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method and an apparatus for controlling output torque of a motor for an electric vehicle in downhill mode. the method comprises following steps: detecting a tilt angle value ?, a current vehicle speed value V and an accelerator-pedal travel value Gain of the vehicle, determining whether the vehicle is in downhill mode or not, and if the result is positive, then calculating a downhill slip torque T1 of the vehicle under the tilt angle value ?, obtaining a maximum output torque T2, calculating an output torque T of the motor based on T1, T2, Gain and a given vehicle speed delimitative value Vref, and controlling the motor to output the calculated output torque T. The present invention ensures the vehicle speed not too high by controlling the output torque of an electric vehicle in downhill mode, even if the brake-pedal travel is zero.