Creep Torque Control for Motor Driven Vehicles
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Solution Overview
Problem
Motor-driven vehicles, such as electric and hybrid vehicles, face challenges in controlling creep torque on downhill inclines, leading to excessive energy consumption and unintentional acceleration due to the trade-off between smooth start and abruptness during braking, which affects ride comfort and fuel efficiency.
Innovation Solution
A method is proposed to calculate a filter time constant based on the downhill gradient, set speed, and basic creep torque, adjusting the torque output to prevent excessive acceleration, involving steps to calculate and apply the time constant to a filter for motor control, ensuring optimal creep torque generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the time constant is reduced to achieve smooth creep departure, then the vehicle can depart smoothly uphill, but the creep torque becomes excessive causing unintentional acceleration on downhill inclines
Solution Approach 1:
The patent applies dynamics by making the filter time constant variable rather than fixed. The time constant is dynamically adjusted based on the downhill gradient detection - when a downhill gradient is detected, the time constant is increased to reduce creep torque, while on flat or uphill surfaces, the smaller time constant is used for smooth departure. This resolves the contradiction by adapting the system behavior to different operating conditions.
Solution Approach 2:
The patent changes the parameter of the filter time constant based on road gradient conditions. By detecting the downhill gradient and adjusting the time constant parameter accordingly, the system optimizes creep torque output for each condition - using a larger time constant on downhills to reduce excessive torque and a smaller time constant on flat/uphill surfaces for smooth departure.
2Ease of operation
If the time constant is increased to reduce abruptness during braking, then ride comfort is improved, but the creep torque becomes excessive consuming more energy
Solution Approach 1:
The system dynamically adjusts the time constant based on real-time gradient detection rather than using a fixed large value. This allows the system to maintain large time constants (for comfort) only when needed on downhill inclines, while using smaller time constants on flat or uphill surfaces to reduce energy consumption, thus resolving the contradiction between comfort and energy efficiency.
Solution Approach 2:
The patent changes the time constant parameter according to operating conditions - using a larger value to improve ride comfort during downhill braking, and a smaller value to reduce energy consumption during normal or uphill operation. This conditional parameter adjustment resolves the trade-off between comfort and energy efficiency.
3Device complexity
If a fixed time constant is used for filtering, then the control system is simple, but it cannot adapt to different road gradients causing either excessive acceleration or energy consumption
Solution Approach 1:
The patent implements feedback by detecting the road gradient condition and using this information to adjust the filter time constant. The gradient detection provides feedback about the operating condition, which is then used to select the appropriate time constant value, enabling the system to adapt to different road gradients while maintaining reasonable complexity through a structured control approach.
Solution Approach 2:
The control system performs self-adjustment by automatically selecting the appropriate time constant based on detected gradient conditions without requiring manual intervention. The system serves itself by using its own gradient detection capability to configure its filtering parameters, balancing adaptability with simplicity.
Data Source
AI summary
A method of controlling creep torque in a motor driven vehicle is disclosed herein. In this method, a downhill gradient of a road is calculated. A filter time constant is calculated using the downhill gradient, a predetermined basic creep torque, a set speed and a compensation coefficient of the predetermined basic creep torque corresponding to the set speed. At a variable control step, the calculated filter time constant is applied to a filter, the predetermined basic creep torque is input to the filter, and a motor is controlled based on a torque value output from the filter as a request torque.