APPLICATION STORY
Assistance that adapts to every step The BEAR-H rehabilitation exoskeleton detects how actively patients participate in gait training and adjusts its assistance accordingly. Compliant joint actuators, a combination of different sensors, and motion control technology make this possible.
Text Fiona Zhang
sors also measure how actively the patient contributes to the movement. The system supplies only the additional force required: the more actively the pa- tient moves, the less assistance the exo- skeleton provides. Detecting movement intention To detect the patient’s movement inten- tion, the BEAR-H combines data from several sensors. Plantar pressure sensors identify the different phases of the gait cycle, while encoders and inertial mea- surement units capture the position and movement of the legs. Together with torque measurements from the joint ac- tuators, these signals allow the control system to recognize when a step is ini- tiated and adjust the assistive torque in real time. A dedicated training mode for stroke patients with hemiplegia allows their own movement to trigger the next step. The drive system uses maxon DCX 35 L and RE 40 motors, controlled by maxon EPOS4 Module 50/15 units. Pre- cise current control allows the motor torque to be adjusted dynamically, en- abling the system to respond quickly and in a controlled manner to the patient’s movements. By combining compliant joint actua- tors, integrated sensing and adaptive motion control, the BEAR-H supports intensive gait training while encourag- ing patients to participate actively.
For people recovering from a stroke, liv- ing with spinal cord injuries, or under- going rehabilitation after orthopedic surgery, relearning to walk can be a long process. Regular, repeatable gait train- ing plays an important role. Conven- tional therapy, however, depends heavily on the experience and physical effort of therapists. Robotic rehabilitation sys- tems can complement their work by sup- porting repeatable movement patterns and adapting the level of assistance to the individual patient. MileBot Robotics, based in Shenzhen, China, develops robotic rehabilitation systems. Its portfolio includes exoskel- etons and gait assistance systems for adults and children. The BEAR-H series is designed for gait training with patients who have impaired lower-limb mobility. Controlled transmission of force At the heart of the system are MileBot’s own Series Elastic Actuators, or SEAs. These actuators incorporate maxon technology. Unlike rigid actuators, they use an elastic element between the motor and the joint. This allows them to absorb forces rather than transmitting them di- rectly to the patient’s body. This is particularly relevant for stroke patients, who may experience a sudden increase in muscle tone or spasticity. In such situations, the elastic structure de- forms reversibly, reducing the force act- ing on the joint. Integrated torque sen-
50
maxon insights # 1
Made with FlippingBook Publishing Software