Mechanical and biomechanical analysis of a linear piston design for angular-velocity-based orthotic control
| Autor: | Jonathan Kofman, Louis Goudreau, Edward D. Lemaire, Reza Samadi |
|---|---|
| Rok vydání: | 2013 |
| Předmět: |
musculoskeletal diseases
Leg Orthotic Devices Engineering business.industry Rehabilitation Context (language use) Equipment Design Walking Knee Joint Swing musculoskeletal system Orthotic device Biomechanical Phenomena Line of action Gait (human) Control system Humans Torque business human activities Simulation Mechanical Phenomena |
| Zdroj: | The Journal of Rehabilitation Research and Development. 50:43 |
| ISSN: | 0748-7711 |
| DOI: | 10.1682/jrrd.2012.02.0031 |
| Popis: | INTRODUCTION Stance-control orthoses (SCOs) are lower-limb assistive devices that prevent knee collapse during weight-bearing while allowing free knee motion during the swing phase of gait [1-18]. The methods of controlling and applying knee-flexion resistance, device complexity, device function, and user acceptance vary considerably between stance-control devices. Many SCOs use the precondition of weight-bearing to engage knee-flexion resistance, with or without a specific lower-limb segment orientation or joint-angle requirement. Mechanical or electromechanical methods are commonly used to detect these preconditions. The devices then apply knee-flexion resistance as appropriate. Unfortunately, the method of applying knee-flexion resistance and the methods of detecting weight-bearing, limb-segment orientation, and joint-angle preconditions may contribute to a complex, bulky, and costly mechanical or electromechanical system. This is especially true if the detection of the precondition and the application of knee-flexion resistance are performed by separate means. Mechanical stance-control knee-ankle-foot orthoses (SCKAFOs) either require full knee extension to lock and unlock the knee or resist knee flexion at any angle. Orthoses that require full knee extension typically use a spring-loaded or weighted pawl to lock the knee in extension when the leg is in a preset position at foot strike [12-13]. While these devices are smaller and lighter than devices that provide resistance at any knee angle, the orthosis cannot stop leg collapse when the person lands with a flexed knee, such as during a stumble or during curb or step navigation. Mechanical SCKAFOs that resist flexion at any knee angle require a mechanism at the foot to determine when the user is weight-bearing [14-16]. These mechanisms include a double-shell ankle-foot orthosis that pushes up on a control rod during weight-bearing, a hinged footplate that engages knee-flexion resistance based on ankle angle, or a pneumatic bladder that engages upon weight-bearing. SCKAFOs with electronic control systems resist knee flexion at any knee angle. Plantar pressure sensors, sometimes combined with position sensors, sense weight-bearing and provide context-based decision-making to control knee-flexion resistance [6-7,11,14,17]. Control electronics and batteries are either housed on the orthoses or in a belt pack. Although electronic control systems can improve stance swing and activity-based mode switching reliability, they add weight, complexity, and power management requirements to the orthotic device. One mechanical method that did not require limb-loading detection used a knee-joint spring to provide an extension moment that decreased as the moment arm shortened during knee flexion [18]. Since the knee extension moment dropped to zero for swing and sitting, knee angle-based stance control was achieved. The orthosis was designed to not resist knee flexion beyond a preset knee angle; however, resistance at any knee angle may be required for stance control in stumbling. Incorporating knee-angle detection inherently in the knee flexion-resistance mechanism, with the spring line of action changing with angle, was a desired feature for minimizing device complexity, weight, bulk, and cost. Another orthosis used inertial, angular-position, and force sensors in a custom actuator system to apply varying stiffness to an orthosis knee joint [10]. Since the system used predetermined relationships between resisting torque and joint angle to switch between stance and swing modes, the device may not handle unexpected conditions such as stumbling. An angular-velocity-based control (AVBC) approach differs from weight-bearing, limb-segment orientation, and joint angle-based control devices by removing the need for mechanical systems or electronic sensors at the foot to maintain safe gait for people with knee-extensor weakness but sufficient hip control [19]. … |
| Databáze: | OpenAIRE |
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