Wheelchair Control System for Speed Maintenance and Voltage Protection
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Solution Overview
Problem
Existing power-assisted wheelchairs face challenges in maintaining speed control at high speeds, requiring excessive user effort due to fast-spinning wheels, and risk electronic component damage from excessive induced voltages during regenerative braking.
Innovation Solution
A control system that adjusts the drive motor's behavior after reaching a limit speed, allowing speed maintenance with reduced handrim deflection and incorporating a protective circuit to prevent voltage-induced damage by short-circuiting excessive voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the wheelchair is driven at high speed, then the drive wheel and handrim spin fast, but the user must deflect the handrim far or fully which requires much faster user input and is very tiring
Solution Approach 1:
The control device dynamically adjusts the motor's run-on time based on the current speed range. When the wheelchair exceeds the limit speed, the control device extends the run-on time of the motor, allowing the handrim to continue rotating without requiring immediate user deflection. This dynamic adjustment reduces the frequency and intensity of user input needed at high speeds.
Solution Approach 2:
The sensor device continuously monitors the wheelchair's speed and provides feedback to the control device. When the limit speed is exceeded, the control device receives this feedback and automatically adjusts the motor's run-on time accordingly. This closed-loop feedback system ensures the motor maintains appropriate run-on characteristics across different speed ranges, reducing user effort at high speeds while maintaining precision at lower speeds.
2Duration of action of moving object
If the motor runs for longer run-on time at higher speeds, then fatigue-free driving is possible, but precise control at low speeds becomes difficult
Solution Approach 1:
The control device implements dynamic run-on time management by adjusting the motor's continuation operation based on the current speed range. At low speeds, the run-on time is kept short to enable precise control and quick response to user input. At high speeds, the run-on time is extended to reduce the frequency of user deflections needed, thereby reducing user fatigue. This dynamic adaptation resolves the contradiction between run-on duration and control precision.
Solution Approach 2:
The control device changes the operational parameters of the motor based on the speed range. Specifically, it adjusts the run-on time parameter: keeping it short at low speeds for precision and extending it at high speeds to reduce user effort. This parameter change strategy allows the system to optimize both control precision and user fatigue reduction across different operating conditions.
3Use of energy by moving object
If the motor acts as a generator during regenerative braking, then energy can be recovered, but excessive induced voltages can destroy sensitive electronic parts
Solution Approach 1:
The invention converts the potentially harmful excessive induced voltage into a beneficial short-circuit path that protects the electronic components. When regenerative braking generates excessive voltage, the control device detects this condition and intentionally creates a controlled short-circuit, dissipating the excess energy safely. This transforms the harmful voltage spike into a protective mechanism that prevents damage to sensitive electronics while maintaining energy recovery functionality.
Solution Approach 2:
The control device implements preliminary protective action by monitoring the induced voltage during regenerative braking and preemptively activating a protection mechanism when voltage thresholds are approached. Before excessive voltage can damage electronic components, the control device intervenes to limit the voltage through controlled short-circuiting. This preliminary anti-action prevents the harmful effect from occurring in the first place.
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
Enables fatigue-free high-speed operation with precise control and protects electronic components from voltage-induced damage, ensuring safe and efficient wheelchair operation.
Implementation Method 1
If, on the other hand, the wheelchair is driven manually or accelerated by gravity when driving downhill, the motor acts as a generator and can recharge the battery.
Data Source
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AI summary
The small-sized vehicle has two running wheels, a sensor device for detecting the manually introduced driving force, a drive motor (34) for running wheels, and a control device for controlling the drive motor depending on the detected manual driving force. The driving behavior of the drive motor is influenced by the control device on reaching a speed limit corresponding to a predetermined limit speed of the vehicle such that the attained speed or speed range is maintained even with reduced tangential deflection of the device for manual application of force with respect to lower speed ranges.