用于膝关节康复外骨骼的阻抗模型预测控制与患者力矩估计
Interaction Dynamics MPC for Knee Rehabilitation Exoskeletons: A Closed-Loop SEA Outer-Loop Study
AI总结：
提出阻抗模型预测控制框架，结合卡尔曼扰动状态估计患者力矩，实现无偏移跟踪和辅助按需，在500 Hz下满足临床精度标准。
摘要：
膝关节康复外骨骼必须强制执行规定的关节轨迹，同时保持对非自主痉挛和自主患者努力的安全顺从——这是任何固定增益阻抗控制器的目标冲突。我们提出了一种用于膝关节康复外骨骼的阻抗模型预测控制框架，并在串联弹性执行器（SEA）平台上进行了演示：代数前馈将膝关节动力学简化为常系数标量双积分器，而滚动时域二次规划（QP）计算校正力矩，同时强制执行硬性的运动范围、力矩和速度限制（ISO 13482）。由直接基于SEA的力矩传感（通过弹性元件测量的串联弹性弹簧挠度——一种固有的、无EMG的患者力矩估计，而非单独的力传感器）驱动的卡尔曼扰动状态提供了标称无偏移保证，并通过其符号和期望运动方向实现无传感器的辅助按需。常状态矩阵允许离线预计算QP成本逆，从而实现多步时域下的500 Hz运行。在七个控制器基准测试（正弦跟踪、等长保持）中，500 Hz卡尔曼MPC在15 Nm痉挛下实现了0.1 mrad RMS、0.1 mrad稳态、0.2 mrad峰值的无偏移，而相同刚度下的经典阻抗控制器稳态偏移为515 mrad——直接测量通道几乎立即（几个采样周期内）收敛估计。没有估计器时，它实现经典阻抗（4.8 mrad RMS，8.3 mrad稳态）。所有MPC变体均满足87 mrad临床标准；没有经典控制器满足。该架构通过考虑耦合的每个关节QP为20自由度MyoSuite myoLeg设计。
英文摘要：
Safe rehabilitation is an interaction-dynamics problem: the controller must regulate a prescribed motion while absorbing involuntary spasm, voluntary effort, actuator compliance, and model mismatch as disturbances. This paper instantiates the predictive interaction-dynamics framework of the base pHRI formulation on a SEA knee joint. SEA feedforward reduces the gravity-compensated knee to the same scalar double integrator as the base framework, while a dynamic-residual measurement from spring deflection supplies an interaction-disturbance observation. A steady-state target converts the estimated disturbance into a cancelling input, and a finite-horizon quadratic program regulates deviations from that target under range-of-motion, torque, and velocity constraints. The evaluation matches stiffness and damping across controllers so gains cannot be attributed to higher impedance. Under a motion-opposing $15\unit{Nm}$ step, classical impedance and MPC without estimation produce about $500\unit{mrad}$ steady-state error, whereas Kalman-augmented interaction MPC reduces this to $1.17\unit{mrad}$ at 100~Hz and $0.70\unit{mrad}$ at 500~Hz; the 500~Hz peak is $7.27\unit{mrad}$. In 30 randomized trials, the 95th-percentile peak is $21.57\unit{mrad}$. Bounded Assist-as-Needed scheduling, a corrective-channel energy tank, constrained OSQP stress cases, direct MuJoCo execution, and a posture-clamped MyoSuite knee slice are implemented. The framework holds on a single-mass, closed-inner-loop SEA approximation; an explicit two-mass plant with a finite-bandwidth, pole-placed inner torque loop (Section~VIII) confirms this for nominal tracking but shows delivered torque can overshoot the commanded bound by 21.7\% near saturation. Scope excludes clinical intent recognition, full-system passivity, safety certification, hardware trials, and multi-joint validation.
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