CONTROL OF END-POINT FORCES OF A MULTIJOINT LIMB BY FUNCTIONAL NEUROMUSCULAR STIMULATION
CONTROL OF END-POINT FORCES OF A MULTIJOINT LIMB BY FUNCTIONAL NEUROMUSCULAR STIMULATION
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DOI：
10.1109/10.88441
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发表时间：
1991-10-01
影响因子：
4.6
通讯作者：
CHIZECK, HJ
中科院分区：
文献类型：
--
作者：
LAN, N;CRAGO, PE;CHIZECK, HJ
设计了一个多变量反馈控制器，并进行了测试，用于调节与等距负载接触的多关节肢体的端点处的力矢量的大小和方向。 力矢量是由肌肉的电刺激产生的。 为了实现任意控制的端点力的大小和方向，两个耦合问题必须处理的控制系统。 首先，在端点力矢量和关节力矩之间存在几何耦合。 力矢量的幅度和方向取决于肢体几何形状。 第二，两个关节处的扭矩可能由于穿过它们的肌肉的激活而耦合（双关节耦合）。 为了消除几何耦合，采用了控制器误差从笛卡尔空间到关节空间的变换。 一个多变量比例积分（PI）控制律被用来计算肌肉激活的基础上转换的控制器误差。 集中和分散控制进行了研究解耦双关节肌肉的影响。 猫的实验结果表明，该控制器可以调节猫后肢末端力的大小和方向。 在强双关节耦合的存在下，集中控制比分散控制在瞬态响应期间产生更好的性能。 两种控制策略都可以在稳态时解耦双关节肌肉。 当不存在双关节耦合时，集中控制有时比分散控制性能差。 这是通过功能性神经肌肉刺激（FNS）同时控制多个关节的第一步。 该控制器在FNS神经假体中具有广泛的应用前景。
A multivariable feedback controller was designed and tested for regulating the magnitude and orientation of the force vector at the end point of a multijoint limb in contact with an isometric load. The force vector was produced by electrical stimulation of muscles. To achieve arbitrary control of end-point force magnitude and orientation, two coupling issues must be dealt with by the control system. First, there is a geometric coupling between the end-point force vector and joint torques. The amplitude and orientation of the force vector depend on the limb geometry. Second, torques at two joints may be coupled due to activation of muscles that cross them (biarticular coupling). To eleminate the geometric coupling, a transformation of controller error from the Cartesian space to the joint space was employed. A multivariable proportional-plus-integral (PI) control law was used to calculate muscle activation based on the transformed controller error. Centralized and decentralized controls were investigated for decoupling the effects of biarticular muscles. The results obtained from cat experiments showed that the magnitude and orientation of the end-point forces of the cat hindlimb could be regulated by this controller. In the presence of strong biarticular coupling, centralized control yielded better performance than decentralized control during transient responses. Both control strategies could decouple the biarticular muscle at steady state. When no biarticular coupling was present, centralized control sometimes performed worse than decentralized control. This is the first step in the simultaneous control of multiple joints by functional neuromuscular stimulation (FNS). The controller has broad potential applications in FNS neural prostheses.