Knee rehabilitation exoskeletons must enforce a prescribed joint trajectory while remaining safely compliant with involuntary spasm and voluntary patient effort-objectives in tension for any fixed-gain impedance controller. We present an Impedance Model Predictive Control framework for knee rehabilitation exoskeletons, demonstrated on a series-elastic-actuator (SEA) platform: an algebraic feedforward reduces the knee dynamics to a constant-coefficient scalar double integrator, and a receding-horizon quadratic program (QP) computes corrective torques while enforcing hard range-of-motion, torque, and velocity limits (ISO 13482). A Kalman disturbance state driven by direct SEA-based torque sensing (the series-elastic spring deflection measured through the elastic element - an intrinsic, EMG-free patient-torque estimate, not a separate load cell) gives a nominal offset-free guarantee and, via its sign and the desired-motion direction, sensorless Assist-as-Needed. The constant state matrix permits offline precomputation of the QP cost inverse, enabling 500 Hz operation with a multi-step horizon. Across seven-controller benchmarks (sinusoidal tracking, isometric hold), the 500 Hz Kalman MPC is offset free 0.1 mrad RMS, 0.1 mrad steady-state, 0.2 mrad peak under 15 Nm spasm, versus a 515 mrad steady-state offset for classical impedance at the same stiffness - the direct-measurement channel converging the estimate near-immediately (within a few sampling periods). Without the estimator it realizes a classical impedance (4.8 mrad RMS, 8.3 mrad steady-state). All MPC variants meet the 87 mrad clinical criterion; no classical controller does. The architecture is formulated for the 20 DOF MyoSuite myoLeg via coupling-aware per-joint QPs.

翻译：膝关节康复外骨骼必须在遵循预设关节轨迹的同时，对非自主痉挛和患者主动用力保持安全顺应性——这对任何固定增益阻抗控制器而言均构成矛盾目标。本文提出一种面向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平台上验证：代数前馈将膝关节动力学简化为常系数标量双积分器，滚动时域二次规划计算修正力矩并强制执行硬约束（活动范围、力矩及速度限值，符合ISO 13482标准）。基于直接串联弹性执行器力矩传感的卡尔曼扰动状态（通过弹性元件测量的串联弹性弹簧形变——这是一种内在的、无需肌电信号的患者力矩估计，而非独立力传感器）提供了无偏名义保证，并通过其符号与期望运动方向实现无传感器辅助按需控制。恒定状态矩阵允许离线预计算二次规划代价逆矩阵，从而在多步预测时域下实现500 Hz运行频率。在七个控制器基准测试（正弦轨迹跟踪、等长保持）中，500 Hz卡尔曼模型预测控制在15 Nm痉挛下达到0.1 mrad均方根误差、0.1 mrad稳态误差及0.2 mrad峰值误差，而相同刚度下的经典阻抗控制稳态误差达515 mrad——直接测量通道在数个采样周期内即可使估计近乎即时收敛。无估计器时系统表现出经典阻抗特性（4.8 mrad均方根误差，8.3 mrad稳态误差）。所有模型预测控制变体均满足87 mrad临床标准，而经典控制器无一达标。该架构通过考虑耦合的逐关节二次规划，适配于20自由度MyoSuite myoLeg平台。