The design of the ALTACRO prototype is a challenge with many requirements. The topics of research demand multiple functionalities of the rehabilitation robot.
- The use of compliant actuation for a safe and soft human-robot interaction
- Active ankle assistance upon assistance of pelvis, hip and knee joints
- A functional gait pattern by providing sufficient (actuated) degrees of freedom
- Safe body-weight support that allows natural gait pattern
- Balance training by compliantly controlled pelvis actuation
Degrees of freedom
A final technically feasible concept was proposed that as far a possible meets the above requirements. In the structure of the ALTACRO gait rehabilitation robot we can distinguish an exoskeleton and a support system, both actuated.
The exoskeleton structure has 8 powered degrees of freedom: hip, knee and ankle flexion/extension as well as ad/abduction of the hip for both legs. The electically powered actuators have an intrinsic mechanical compliance (see MACCEPA) and are fully integrated in the exoskeleton structure for a light-weight design.
The support system contain 5 actuated degrees of freedom that act on both exoskeleton legs at the height of the pelvis. It can provide full body weight while it is also capable of allowing and assisting in a functional gait pattern using a compliant control algorithm based on force sensors. The support structure can actuate lateral, sagittal and vertical translation of the pelvis, internal/external rotation and pelvic obliquity.