Train Speed Control Using Regenerative Braking
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Solution Overview
Problem
In railway systems, vehicles equipped with ATP devices experience worsened riding comfort due to frequent acceleration limit violations, leading to undershoots and overshoots in speed changes, which increase traveling time.
Innovation Solution
An automatic train driving apparatus that includes a speed control unit with upper and deceleration target speed generation units, a minimum value selection unit, mass multiplication, traction force restriction, and motor command generation, which calculates and controls target speed transition patterns using regenerative brake forces to optimize acceleration and deceleration, ensuring comfortable and efficient travel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If acceleration limits are imposed based on motor performance and jerk limits are applied to ensure riding comfort, then riding comfort is improved, but the change rate of vehicle acceleration frequently reaches the limit, causing undershoot and overshoot in speed changes
Solution Approach 1:
The system performs preliminary calculation of target acceleration values considering future speed pattern requirements and current vehicle state. By predicting future acceleration needs and preparing appropriate target values in advance, the system can smoothly transition between acceleration levels without reaching limiting values, thereby avoiding undershoot and overshoot while maintaining riding comfort and reducing traveling time.
2Manufacturing precision
If upper speed limit and acceleration restrictions are applied to track the speed pattern, then speed control precision is improved, but the change rate of vehicle acceleration frequently reaches the limit, worsening riding comfort
Solution Approach 1:
The system dynamically adjusts target acceleration values based on real-time vehicle state (current speed, current acceleration) and future speed pattern requirements. This dynamic adjustment allows the system to maintain speed control precision by adapting target acceleration to current conditions, preventing the change rate from frequently reaching limits and thus maintaining riding comfort while tracking the speed pattern accurately.
3Loss of energy
If regenerative brake force is used for deceleration control, then energy efficiency is improved, but the brake force characteristic varies with vehicle speed, requiring complex control
Solution Approach 1:
The system changes the control parameter from fixed deceleration commands to speed-dependent target acceleration values that account for regenerative brake force characteristics. By calculating target acceleration based on current vehicle speed and the known relationship between speed and regenerative brake force, the system adapts to the varying brake force characteristics without requiring complex control mechanisms, thereby maintaining energy efficiency while simplifying control.
Data Source
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AI summary
In an automatic train driving apparatus provided in a vehicle, a speed control unit controls the deceleration of the speed of the vehicle using the braking force of only the regenerative brake in accordance with the speed of the vehicle based on a target speed pattern calculated using the brake force characteristics of the regenerative brake when a notification indicating that the vehicle has approached a stop limit position is received by an external device, and when the vehicle travels at a speed equal to or higher than the brake force characteristic decreasing speed at which the brake force characteristic of the regenerative brake decreases by having the brake decreasing speed or higher in the brake force characteristic indicating a relationship between the speed of the vehicle and the decreasing speed thereof per unit time when the speed of the vehicle is controlled in a deceleration manner with the maximum brake force of the regenerative brake.