Safe Torque Off Circuit for Motor Braking During Battery Disconnect
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Solution Overview
Problem
In electric vehicles, particularly during a tip-over event, the loss of power can cause electric motors to continue spinning due to inertia, posing safety risks as the control systems may fail to stop the motors effectively if the battery disconnects, leading to prolonged spinning of cutting blades in lawnmowers and other devices.
Innovation Solution
A safe torque off circuit with a backup power source and feedback inputs is implemented to provide a switch signal to the motor circuit, ensuring the motor stops even during battery disconnection by shorting phases and dissipating energy as heat, thus controlling the motor's kinetic energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the battery is disconnected during a turn over event, then the control system loses power and cannot perform controlled stop, but the motor continues to spin due to inertia creating safety risks
Solution Approach 1:
A backup power source is pre-configured in the safe torque off circuit to provide power specifically for motor stoppage functions during battery disconnect events. This preliminary preparation ensures that when the main battery disconnects, the motor can still be stopped reliably without requiring a fully redundant control system.
Solution Approach 2:
The safe torque off circuit is extracted as a separate, independent subsystem with its own backup power source, isolated from the main control system. This allows the motor stoppage function to operate independently even when the main control system loses power, resolving the contradiction by providing reliability without requiring the entire control system to be complex and redundant.
2Ease of manufacture
If the control system is simplified to reduce complexity, then the system becomes easier to manufacture and maintain, but the ability to stop motors during power loss events is compromised
Solution Approach 1:
The control system is segmented into two independent parts: the main control system and the safe torque off circuit with backup power. This segmentation allows the safe torque off function to be manufactured and maintained as a separate, simpler module while ensuring reliability during power loss events. The segmented architecture reduces overall manufacturing complexity compared to a fully integrated redundant system.
3Device complexity
If the motor is allowed to spin down naturally during battery disconnect, then no additional components are needed, but the prolonged spinning creates safety hazards
Solution Approach 1:
The backup power source in the safe torque off circuit converts the harmful situation of uncontrolled motor spinning into a beneficial controlled stoppage. By providing just enough power to activate the safe torque off circuit, the system transforms the hazard of prolonged spinning into a controlled energy dissipation process, eliminating safety hazards while adding minimal components.
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
This solution effectively stops the motor blades by converting kinetic energy into heat, ensuring safety by preventing prolonged spinning and maintaining control over the motor even when the primary power source is disconnected.
Implementation Method 1
shorting phases and dissipating energy as heat, thus controlling the motor's kinetic energy
Data Source
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AI summary
In one embodiment, an apparatus for motor stoppage during a battery disconnect includes a safe torque off circuit, a backup power source, and a feedback input. The backup power source is configured to supply power to the safe torque off circuit. The feedback input is configured to provide a status signal to the safe torque off circuit. The safe torque off circuit is configured to provide a switch signal to a motor circuit in response to the status signal.