EV Hill Hold Torque Control for Position Oscillation Suppression
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Solution Overview
Problem
Conventional hill hold functions in electric vehicles do not accurately oppose load torque, leading to undesirable vehicle position oscillations and rollback when driving on uphill grades.
Innovation Solution
A hill hold function that accounts for vehicle weight, drive shaft stiffness, and road grade to precisely generate motor torque, utilizing a resonance suppression control circuit with an extended state observer and PID controller to reduce or eliminate position oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If motor torque is applied to oppose load torque during hill hold, then vehicle position stability is improved, but position oscillations occur due to inaccurate torque opposition
Solution Approach 1:
The system employs an extended state observer to continuously monitor vehicle position and estimate load torque, feeding this information back to the PID controller which adjusts motor torque in real-time. This closed-loop feedback mechanism enables precise torque opposition that counteracts oscillations while maintaining position stability during hill hold operation.
Solution Approach 2:
The PID controller dynamically adjusts motor torque parameters based on real-time vehicle position and estimated load torque conditions. By continuously optimizing torque magnitude and timing parameters, the system achieves accurate opposition to load torque without causing oscillations, resolving the contradiction between stability and harmful oscillations.
2Reliability
If conventional hill hold function is used, then vehicle position is maintained, but oscillations and rollback occur due to inaccurate load torque opposition
Solution Approach 1:
The system replaces conventional mechanical brake-based hill hold with an electric motor torque-based system. The motor torque is precisely controlled through electronic feedback from the extended state observer and PID controller, enabling accurate opposition to load torque and eliminating the position control precision problems inherent in mechanical systems.
Solution Approach 2:
The extended state observer acts as an intermediary that estimates load torque based on vehicle position and other sensor data, providing this information to the PID controller. This intermediary estimation mechanism enables more precise torque control than direct measurement, improving both reliability and position control precision.
3Stability of the object's composition
If motor torque is increased to prevent rollback, then vehicle position stability improves, but oscillations are exacerbated
Solution Approach 1:
The PID controller dynamically adjusts motor torque based on real-time vehicle position feedback and estimated load torque conditions. Rather than applying fixed or excessive torque, the system continuously optimizes torque magnitude to match actual load conditions, providing just enough force to maintain stability without inducing oscillations.
Solution Approach 2:
The extended state observer continuously monitors vehicle position and estimates load torque, feeding this information back to the PID controller. This feedback loop enables the system to detect and correct position deviations in real-time with precise torque adjustments, maintaining stability without the need for excessive torque that would cause oscillations.
Data Source
AI summary
Methods and apparatus for hill hold in an electric vehicle are disclosed. In one embodiment, a system includes a motor and a controller operable in a hill hold control mode. The motor is coupled to one or more wheels of a vehicle. In the hill hold control mode, the controller controls the motor to generate a holding torque to maintain a vehicle speed at zero. The holding torque prevents a change in vehicle position. The holding torque opposes changes in the road grade, the shaft stiffness, or the vehicle weight to prevent oscillations in the vehicle position. The controller uses at least one of road grade, shaft stiffness, and vehicle weight to control the motor to generate the holding torque. The hill hold control mode operates across a range of vehicle weights, a range of shaft stiffnesses, and a range of road grades, without additional tuning of the controller.