Motor Control Circuit Undervoltage Management for Brake Systems
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Solution Overview
Problem
Existing brake systems for electric vehicles face issues with extreme undervoltage during engine startup, leading to potential damage from hydraulic pressure, slipping clutch damage, and loss of control over the motor due to rapid discharge of intermediate circuit capacitance.
Innovation Solution
A control method for a multiphase motor using a control circuit with multiple transistors in first and second paths, employing normal, first drive, and third drive modes, and alternating between these modes to manage undervoltages and overvoltages, preventing unintentional actuator pushback and protecting electrical components by maintaining intermediate circuit voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the linear actuator operates in normal mode with hydraulic pressure building up, then the braking function is achieved, but the intermediate circuit capacitance is quickly discharged causing undervoltage
Solution Approach 1:
The control method detects undervoltage conditions before they reach critical levels and preemptively switches to the first drive mode, short-circuiting all transistors of the second paths to prevent complete capacitance discharge and maintain sufficient voltage for gate driver unit operation
Solution Approach 2:
The system dynamically switches between three different drive modes (normal, first drive mode, second drive mode) based on real-time voltage monitoring, adjusting the transistor switching states to optimize both braking performance and voltage maintenance
2Adaptability or versatility
If the combustion engine is started while pressure is building up, then the engine can be started, but extreme undervoltage occurs leading to control shutdown
Solution Approach 1:
The control circuit continuously monitors the intermediate circuit voltage and provides feedback to the drive mode selection logic, enabling real-time adaptation when engine startup causes voltage drops and preventing control shutdown by maintaining voltage above critical thresholds
Solution Approach 2:
The system detects undervoltage conditions caused by engine startup and preemptively activates the first or second drive mode to maintain sufficient voltage levels, preventing the control system from shutting down during the startup process
3Ease of operation
If the linear actuator is pushed back by hydraulic pressure, then the actuator reaches the end stop, but the slipping clutch can be damaged
Solution Approach 1:
The control method applies preliminary anti-action by detecting undervoltage conditions and switching to protective drive modes before the actuator can be pushed back to the end stop, preventing the mechanical damage that would otherwise occur from excessive reverse force on the slipping clutch
4Use of energy by moving object
If all transistors are opened in the third drive mode, then the intermediate circuit voltage can be maintained, but the motor control is lost
Solution Approach 1:
The system dynamically selects between the second drive mode (alternating operation for voltage maintenance) and the third drive mode (all transistors opened for voltage preservation) based on the severity of undervoltage conditions, balancing voltage maintenance with retained motor control capability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents damage to the slipping clutch and electrical components by managing undervoltages and overvoltages, ensuring stable motor control and pressure regulation, and maintaining sufficient power supply to the gate driver unit.
Implementation Method 1
operating the drive circuit in the first drive mode if a first undervoltage was detected and operating the drive circuit in the second drive mode if a second undervoltage was detected
Data Source
Figure 1~2
AI summary
The invention relates to a method for controlling a multi-phase motor by means of a control circuit, in which the control circuit comprises a plurality of transistors, and a first path and a second path are provided for each phase of the motor, at least one transistor being respectively associated with the first and the second path of the different phases, and a normal mode (N), a first control mode (A1) and a third control mode (A3) are provided, all of the transistors of the second path being short-circuited for the first control mode (A1) and all of the transistors being opened for the third control mode (A3), a second control mode (A2) being provided in which an alternate operation between the first control mode (A1) and the third control mode (A3) takes place, the following steps being carried out: detecting an undervoltage (U1, U2, U3) or an overvoltage (UES) in the control circuit; operating the control circuit in the first control mode (A1) when a first undervoltage (U1) has been detected, and operating the control circuit in the second control mode (A2) when a second undervoltage (U2) has been detected. The invention also relates to a control circuit for controlling the motor, to a brake system comprising such a control circuit, and to the use of the control circuit in a brake system.