Electric Motor Braking Torque Control for Emergency Vehicle Deceleration
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Solution Overview
Problem
Conventional vehicle braking methods require a long time to initiate braking, leading to extended braking distances, especially in emergency situations, due to limitations in motor braking torque and the delayed responsiveness of hydraulic braking systems.
Innovation Solution
The method involves controlling the electric motor to exceed its nominal load capacity temporarily during overload operation, allowing for increased motor braking torque, which is synchronized with the hydraulic braking system to reduce braking distance, while preventing overheating and damage by limiting the overload duration and adjusting based on friction torque and wheel slip detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the electric motor is operated above nominal load capacity to increase motor braking torque, then braking distance is shortened, but the electric motor may overheat or be damaged
Solution Approach 1:
The control device dynamically adjusts the motor braking torque based on real-time monitoring of motor temperature and load conditions. The system transitions from static nominal load operation to dynamic overload operation when safety conditions are met, allowing temporary exceedance of nominal load capacity during emergency braking while preventing damage through continuous adaptation to changing thermal and mechanical states
Solution Approach 2:
The system changes operational parameters by allowing the motor to operate above its nominal load capacity under controlled conditions. The control device modifies the motor braking torque parameter from its standard limited value to an elevated value during emergency braking, while simultaneously monitoring temperature parameters to ensure the motor remains within safe operational envelopes despite the parameter change
2Reliability
If the electric motor is controlled to remain below nominal load capacity, then the electric motor is protected from damage, but braking distance increases
Solution Approach 1:
The system applies partial overload action by allowing the motor to operate above nominal load capacity only to the extent necessary for emergency braking, rather than continuously. The control device permits temporary excessive motor braking torque during critical situations while maintaining normal operational limits during routine driving, achieving the beneficial effect of shortened braking distance without subjecting the motor to sustained damaging conditions
3Device complexity
If hydraulic braking system is used alone, then the braking system is simple, but the response time is long (approximately 700 ms)
Solution Approach 1:
The system merges two braking mechanisms into a coordinated dual-braking system: the hydraulic braking system and the electric motor braking system. The control device integrates both systems so that the electric motor provides immediate braking response while the hydraulic system builds pressure simultaneously, combining the rapid response of electric braking with the proven reliability of hydraulic braking to achieve both speed and simplicity
Data Source
AI summary
A method for operating an electric motor for braking a vehicle, including controlling the electric motor in such a way that the vehicle is slowed or decelerated with the aid of a motor braking torque exerted by the controlled electric motor. The method includes ascertaining whether a requested setpoint speed change is in a predefined normal range, and if so, the electric motor is controlled in such a way that a load to be applied by the electric motor remains less than or equal to a nominal load capacity of the electric motor. If the requested setpoint speed change is outside the predefined normal range, the electric motor is controlled in such a way that the load to be applied by the electric motor exceeds the nominal load capacity of the electric motor, at least during a predefined overload operation time interval.