System for controlling an exoskeleton haptic device for rehabilitation purposes, and corresponding exoskeleton haptic device

Control system for an exoskeleton haptic device, said exoskeleton haptic device having:

• a frame structure, configured to be coupled to the body of a subject;
• actuator means, carried by said frame structure and operable to cause movement of a number of joints of said body;
• first sensor means, coupled to said body and configured to detect first signals (yo) indicative of an intention of movement of said subject, characterized by comprising:
• a feedback stage, configured to control a position of said joints based on a reference position (θref) and joint position and velocity measures (θ,{dot over (θ)});
• a feedforward stage, configured to control a compliance presented by said exoskeleton haptic device to said subject based on the detected first signals (yo);
• and
• combining means, configured to combine outputs from said feedback stage and feedforward stage in order to generate a driving signal (um) for said actuator means, thereby imposing a controlled position (θ) to said joints,
• wherein said feedforward stage includes an admittance block configured to control an admittance response of said exoskeleton haptic device in a neighbor of the reference position (θref) with respect to a subject effort (C0);
• wherein said compliance is achieved through said admittance control;
• and
• wherein said feedback stage and feedforward stage are configured to implement a primary closed loop for control of said position of said joints and of said compliance;
• further comprising a secondary closed loop, operatively coupled to said primary closed loop for control of postural equilibrium of said subject during said movement, and wherein said secondary closed loop is configured to generate a perturbation (δθref) of said reference position (θref) at input of said feedback stage such as to maintain said postural equilibrium;
• second sensor means configured to detect reaction forces imparted by the ground to said subject and a center of said reaction forces;
• wherein said secondary closed loop is configured to:
• implement an inverted pendulum model of said exoskeleton haptic device;
• estimate a position of the zero moment point (ZMP) of said body, which is the point at which a resultant of torques associated to said reaction forces is zero, and a position of the COG—center of gravity—of said body, based on signals detected by said second sensor means;
• and
• determine a value of said perturbation (δθref), such that said ZMP position is maintained in a region of postural stability controlling said COG position;
• and
• an inhibitor block configured to perform a determination whether equilibrium limits have been reached, based on a determined ZMP position, and to inhibit operation of said feedforward stage based on said determination, by increasing a stiffness in an imposed admittance.