Wheelchair Steering Correction via Caster Sensor Feedback
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Solution Overview
Problem
Conventional wheelchair steering systems face challenges in maintaining accurate trajectory and stability, particularly during turns, due to differences between commanded and computed yaw rates, which can lead to veering or wheel slip conditions.
Innovation Solution
A wheelchair system with a controller that receives signals from user input devices and caster sensors to determine multiple turn rate parameters, adjusting motor parameters of left and right drive wheels to maintain a selected trajectory by comparing commanded and computed yaw rates, and reducing wheel velocities proportionally to yaw rate differentials to compensate for slippage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional wheelchair steering systems are used, then the structure is simple, but the trajectory accuracy deteriorates due to differences between commanded and computed yaw rates
Solution Approach 1:
The patent implements a feedback mechanism where the controller continuously compares the commanded yaw rate (from user input) with the computed yaw rate (from caster sensor and motor parameters). Based on the difference between these two values, the controller automatically adjusts motor parameters to correct trajectory deviations, thereby improving trajectory accuracy through closed-loop control
Solution Approach 2:
The controller performs multiple functions: it processes user input signals, reads caster sensor data, computes yaw rates, compares commanded and computed values, and adjusts motor parameters. This multi-functionality allows a single device to handle both steering control and trajectory correction, improving accuracy without proportionally increasing system complexity
2Manufacturing precision
If motor parameters are adjusted to maintain trajectory, then trajectory accuracy is improved, but the risk of wheel slip increases during turns
Solution Approach 1:
The patent dynamically changes motor parameters (current, voltage, or speed) based on the difference between commanded and computed yaw rates. During turns, the controller adjusts these parameters in real-time to maintain the desired trajectory while monitoring for conditions that could cause wheel slip, thereby balancing trajectory accuracy with slip prevention
Solution Approach 2:
The system takes preliminary anti-action by continuously monitoring the difference between commanded and computed yaw rates and adjusting motor parameters before wheel slip occurs. The controller proactively compensates for potential slip conditions by modifying motor output based on predicted trajectory deviations, preventing slip rather than reacting after it occurs
3Manufacturing precision
If multiple turn rate parameters are calculated, then steering accuracy is improved, but the computational load increases
Solution Approach 1:
The patent calculates multiple turn rate parameters (first turn rate from user input and caster angle, second turn rate incorporating lateral acceleration, and third turn rate as their average) to improve steering accuracy. This partial use of multiple calculation methods provides sufficient accuracy improvement without requiring all possible computational approaches, balancing precision with manageable computational load
Data Source
AI summary
In one embodiment, a wheelchair includes a drive wheel, a motor coupled to the drive wheel, and a user input device. The motor, in one embodiment, is configured to rotate the drive wheel. The user input device may be configured to send a signal for controlling a motor parameter. The wheelchair, in one embodiment, includes a caster wheel and a castor sensor configured to sense a caster angle. In one embodiment, a controller is configured to receive the signal for controlling the motor parameter and a signal from the caster sensor and to determine a first turn rate parameter of the wheelchair based upon the received signal from each of the input device and the caster sensor.