Vehicle Speed Control Apparatus with Variable Gain Feedback
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Solution Overview
Problem
Existing vehicle speed control systems face challenges with nonlinear vehicle characteristics, leading to oversensitive or slow accelerator operations due to varying engine torque, gear ratios, and tire deformation, which affect sensitivity and response at different vehicle states.
Innovation Solution
A vehicle speed control apparatus that calculates an inverse number of vehicle sensitivity using a driving force characteristic map, adjusts the accelerator opening angle based on this sensitivity, and employs a PI control with varying gains to improve responsiveness and following properties across different vehicle states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed gain is used in PI control for vehicle speed deviation, then the control system is simple to implement, but the accelerator operation becomes oversensitive at low-speed states and slow at high-speed states due to nonlinear vehicle characteristics
Solution Approach 1:
The patent applies dynamics by making the feedback gain variable rather than fixed. The gain is dynamically adjusted based on the vehicle state (accelerator opening angle and vehicle speed) to match the nonlinear characteristics of the vehicle. This allows the control system to adapt its responsiveness to different operating conditions, preventing oversensitivity at low speeds and improving response at high speeds.
Solution Approach 2:
The patent changes the parameter of feedback gain from a constant value to a variable value that depends on vehicle state. By calculating the gain based on accelerator opening angle and vehicle speed, the system adjusts the control parameter to compensate for nonlinear vehicle characteristics, thereby improving accelerator operation responsiveness across different states.
2Reliability
If the vehicle speed feedback gain is increased to improve following property at high-speed states, then the vehicle speed tracking improves, but the accelerator operation becomes oversensitive at low-speed states
Solution Approach 1:
The patent applies local quality by providing different feedback gains for different vehicle states. Instead of using a uniform gain across all conditions, the system calculates state-specific gains based on accelerator opening angle and vehicle speed. This allows high-speed states to receive higher gains for better following property while low-speed states receive lower gains to prevent oversensitivity.
Solution Approach 2:
The feedback gain parameter is changed from a fixed value to a variable value that adapts to vehicle state. The gain calculation incorporates accelerator opening angle and vehicle speed to ensure appropriate responsiveness at each operating condition, thereby eliminating the trade-off between following property and oversensitivity.
3Object-affected harmful factors
If the vehicle speed feedback gain is decreased to prevent oversensitivity at low-speed states, then the accelerator operation becomes stable, but the vehicle speed following property deteriorates at high-speed states
Solution Approach 1:
The system uses dynamic gain adjustment based on real-time vehicle state rather than a fixed low gain. The gain is calculated to be low at low-speed states (preventing oversensitivity) and high at high-speed states (improving following property), thereby resolving the contradiction through state-dependent adaptation.
Solution Approach 2:
The feedback gain parameter is varied according to vehicle state (accelerator opening angle and speed). This parameter change ensures that the gain is appropriately low when needed to prevent oversensitivity and appropriately high when needed to improve following property, eliminating the need to choose between the two extremes.
Data Source
AI summary
A vehicle speed control apparatus including a driving force characteristic map section configured to have a previously recorded driving force characteristic map, to input a target driving force and a target vehicle speed, and to output an accelerator opening angle in accordance with the driving force characteristic map, a vehicle sensitivity calculating section configured to calculate an inverse number of a vehicle sensitivity in accordance with the driving force characteristic map, a vehicle speed feedback section configured to input a vehicle speed deviation and the inverse number of the vehicle sensitivity and to output an accelerator opening angle according to the inverse number of the vehicle sensitivity, and an addition section configured to add the accelerator opening angle from the driving force characteristic map section to the accelerator opening angle from the vehicle speed feedback section to provide an accelerator opening angle command.