Body Weight Support System with Multi-Cable Actuation
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Solution Overview
Problem
Current body weight support systems for gait rehabilitation and training are inadequate as they fail to provide selective positive and negative counterweight forces, leading to instability and inability to simulate real-life scenarios effectively, especially in situations requiring forces in directions other than the vertical axis.
Innovation Solution
A body weight support system utilizing a harness coupled with multiple cables and actuators, along with force and motion sensors, to dynamically adjust tensions in the cables, allowing for algebraic addition or removal of body weight in both steady-state and transient modes, providing forces in X, Y, and Z directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cable-suspended passive counter-weight mechanism is used to reduce subject's body weight, then the subject can walk with disabled legs during training, but the system fails to provide accurate body weight support during transient phases due to inertia forces on the counter weight
Solution Approach 1:
The patent replaces the passive mechanical counter-weight system with an actively-controlled cable-suspended system using actuators (motors) to generate and control tension forces. This substitution allows the system to dynamically compensate for inertia forces and provide accurate body weight support during both steady-state and transient phases of gait training, eliminating the fundamental limitation of passive counter-weight mechanisms.
Solution Approach 2:
The patent implements a dynamic control system where actuators continuously adjust cable tensions based on real-time measurements of subject acceleration and gait phase. The controller calculates required tension forces to compensate for both gravitational weight and inertial effects, enabling the system to adapt to irregular and accelerating movements that occur during early-stage gait rehabilitation training.
2Ease of operation
If a cable-suspended passive counter-weight mechanism is used, then the system structure is simple, but the counter weight has to be manually adjusted to provide selective counterweights during rehabilitation
Solution Approach 1:
The patent implements a self-adjusting control system that automatically determines and applies the appropriate counterweight force based on real-time sensing of subject acceleration, gait phase, and desired body weight support level. The controller continuously calculates and adjusts cable tensions without manual intervention, allowing rehabilitation professionals to select target support levels while the system handles all dynamic adjustments automatically during training sessions.
Solution Approach 2:
The patent employs feedback control using accelerometers and force sensors to monitor subject motion and cable tensions in real-time. The controller uses this feedback information to continuously adjust actuator outputs, ensuring accurate body weight support compensation during both steady-state walking and transient phases. This closed-loop control eliminates the need for manual counterweight adjustments while maintaining system simplicity for the user.
3Adaptability or versatility
If an actively-controlled cable-suspended BWS system is used to provide perfect force in vertical direction, then the subject feels reduced body weight equal to prescribed amount, but the system cannot provide forces in directions other than vertical direction
Solution Approach 1:
The patent extends the force application capability from one dimension (vertical only) to three dimensions by incorporating multiple cables arranged in different spatial orientations. Each cable can generate tension forces in its specific direction, and the combined effect of multiple cables provides full three-dimensional force control. This allows the system to apply forces not only in the vertical direction but also in horizontal and lateral directions, enabling more versatile gait training and balance rehabilitation.
4Adaptability or versatility
If multiple cables with actuators are used to provide three-dimensional force control, then the system can provide forces in X, Y, and Z directions, but the device complexity increases
Solution Approach 1:
The patent designs a multi-cable system where each cable and actuator combination serves multiple functions: providing body weight support in the vertical direction, generating horizontal forces for balance training, and contributing to three-dimensional force control. This universal design allows the same actuator system to handle various rehabilitation tasks and training scenarios, justifying the increased device complexity through enhanced versatility and multi-functionality.
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 system enables stable and realistic simulations by compensating for inertia forces and providing selective counterweight forces, enhancing the effectiveness of gait rehabilitation and training by mimicking real-life movements and environments.
Implementation Method 1
an actuator for each of the plurality of cables, each actuator configured to place a tension on a corresponding cable in response to an electrical signal
Implementation Method 2
at least one force sensor configured to provide an electrical signal corresponding to forces applied to the harness
Implementation Method 3
at least one motion sensor configured to provide an electrical signal corresponding to changes in acceleration of the subject
Implementation Method 4
calculating instantaneous tensions to be placed on each of the plurality of cables in accordance with a user's input data... a transient body weight to be algebraically added to or removed from the subject
Data Source
AI summary
A body weight support (BWS) system is disclosed. The BWS system includes a harness coupled to a plurality of cables, wherein the harness is worn by a subject, an actuator for each of the plurality of cables, each actuator configured to place a tension on a corresponding cable in response to an electrical signal, at least one force sensor configured to provide an electrical signal corresponding to forces applied to the harness, at least one motion sensor configured to provide an electrical signal corresponding to changes in acceleration of the subject, and a controller configured to control the plurality of actuators.