Gait Training Apparatus Wire Force Control
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Solution Overview
Problem
Gait training apparatuses with gait assist devices experience hunting phenomena due to oscillations in weight-bearing force, particularly during transitions between swing and stance phases, which can burden users and hinder effective training.
Innovation Solution
A gait training apparatus equipped with a wire system that adjusts pulling force based on detected speed and leg movement phases, using a motor and control unit to maintain a predetermined force during phase transitions and adjust dynamically based on frictional forces to minimize oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a wire system with motor and housing mechanism is used to bear the weight of the gait assist device, then the burden on the trainee is reduced, but hunting (oscillation of weight-bearing force) occurs during leg movement transitions
Solution Approach 1:
The control unit dynamically adjusts the motor's pulling force based on real-time speed detection. When the wire retraction/release speed falls within a prescribed range (indicating phase transition), the control unit sets the pulling force to a predetermined value independent of speed, thereby stabilizing the weight-bearing force and preventing hunting oscillations.
Solution Approach 2:
The speed detecting unit continuously monitors the wire retraction/release speed and feeds this information back to the control unit. The control unit uses this feedback to determine whether the leg is in swing or stance phase and accordingly adjusts the motor's pulling force to maintain stability during phase transitions.
2Force
If the pulling force is adjusted based on wire retraction speed, then dynamic friction and viscous friction are compensated, but hunting occurs during phase transitions when speed is near zero
Solution Approach 1:
The control strategy applies different force adjustment rules to different operational conditions. When the wire speed is within the prescribed range (phase transition period), the pulling force is set to a predetermined value independent of speed. When the wire speed is outside this range (normal operation), the pulling force is adjusted based on speed to compensate for friction. This localized differentiation resolves the contradiction between force accuracy and stability.
3Force
If the motor applies speed-dependent pulling force to compensate for friction, then the weight-bearing force is maintained during normal movement, but oscillations occur during swing-stance phase transitions
Solution Approach 1:
The system dynamically switches between two control modes: speed-dependent force adjustment for normal operation (to compensate friction) and speed-independent predetermined force during phase transitions (to prevent oscillations). This dynamic switching ensures both proper force maintenance and training comfort.
Solution Approach 2:
The control unit changes the functional relationship between speed and pulling force based on the detected operational phase. During phase transitions (speed within prescribed range), the pulling force parameter is changed to be independent of speed. During normal operation (speed outside prescribed range), the pulling force parameter follows a speed-dependent relationship to compensate for frictional effects.
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
The apparatus effectively reduces hunting of weight-bearing force oscillations, providing a stable and consistent weight-bearing force, thereby enhancing user comfort and training efficiency.
Implementation Method 1
the influence of a dynamic friction and a viscous friction is cancelled out to provide a certain magnitude of weight-bearing force
Implementation Method 2
a speed detecting unit configured to detect a speed at which the housing mechanism retracts or releases the wire
Implementation Method 3
The control unit is configured to control the motor such that the pulling force is adjusted to a predetermined pulling force that is independent of the speed, when the speed is within a prescribed range defined in advance and including zero
Data Source
AI summary
A gait training apparatus includes a wire configured to directly or indirectly pull a trainee's leg fitted with a gait assist device from a position above the trainee's head; a control unit configured to control a motor that applies a pulling force to the wire, thereby adjusting the pulling force; and a housing mechanism configured to retract or release the wire in response to a motion of the leg. The control unit controls the motor such that the pulling force is adjusted to a predetermined pulling force that is independent of the speed, when a speed at which the housing mechanism retracts or releases the wire is within a prescribed range defined in advance and including zero. The control unit controls the motor such that the pulling force is adjusted to a pulling force calculated based on the speed, when the speed is out of the prescribed range.