INSTRUMENTED CRUTCH

The instrumented crutch can help the control of a robotic exoskeleton by acting as an external intention and stability sensor. For example, an ankle exoskeleton normally senses only what happens at the ankle, such as joint angle, velocity, and torque. However, when a user walks with crutches, a large part of the walking strategy is expressed through the crutch: when it touches the ground, how much weight the user puts on it, and in which direction the crutch is oriented.

We have develped a device that measures axial crutch force, crutch orientation using the 6-axis IMU, and estimates force components Fx, Fy, and Fz. For an ankle exoskeleton, this information can be used to detect gait phase and user intent. For example, when the crutch force suddenly increases, the controller can infer that the crutch is in contact with the ground and that the user is preparing to transfer weight, initiate a step, or stabilize themselves. If the crutch is inclined forward and loaded, it may indicate forward progression intent. If the crutch is loaded laterally, it may indicate balance correction or instability. This can help the ankle exoskeleton decide when to provide dorsiflexion support, when to increase ankle stiffness for stance stability, and when to prepare for plantarflexion assistance during push-off. If the crutch force is low and the gait pattern is stable, the controller can allow more natural ankle motion or provide more active assistance. In other words, crutch loading can be used as a real-time confidence or stability indicator.