Rehabilitation Robot Arm Product

Overview

A rehabilitation robot arm delivers the raw material of motor recovery after stroke or neurological injury: hundreds of repetitions of guided arm movement per session, far more than a therapist can provide hands-on. The clinical basis is neuroplasticity — intensive, repetitive, task-oriented practice drives cortical reorganization, and dose matters. A therapist can manually guide perhaps 30 to 60 movements before fatiguing; the robot sustains 600 to 1000 per session while measuring every one of them.

The machine is an exoskeleton: its Arm Linkage runs alongside the patient's arm with joints aligned to the anatomical ones, so it can control the shoulder, elbow, and wrist individually rather than just dragging the hand around. A three-axis Shoulder Gimbal of nested Gimbal Rings intersects at the shoulder centre; telescoping Upper-Arm Link and Forearm Link segments adjust to the patient's limb lengths; the Elbow Joint and Wrist Module complete five powered degrees of freedom. Gravity Compensation Spring elements cancel the linkage's own weight so the motors spend their authority on therapy, not on holding up aluminium.

Why series-elastic actuation

Every joint uses the same Series-Elastic Joint Drive: a frameless Servo Motor through a deliberately low Helical Gear Pair ratio, with a machined Torsion Spring Element in series between gearbox and output. Two Encoders — motor side and output side — measure the spring's twist, which gives joint torque directly to 0.1 N·m. This is the standard architecture for robots that touch people. A stiff high-ratio joint is a position source: it goes where commanded and crushes whatever objects. A series-elastic joint is a torque source: the controller commands force, the spring filters impacts, and the low gearing keeps the joint backdrivable, so a patient (or a falling patient) can always overpower it. The cost is control bandwidth, which therapy — slow, smooth movements — does not miss.

Assist-as-needed control

The Real-Time Control Board closes impedance loops at 1 kHz: rather than tracking a trajectory rigidly, each joint behaves like a programmable spring-damper pulling gently toward the target path. Patient effort is measured at the Cuff Load Cells between the cuffs and the linkage, the Grip Force Sensor in the handle, and optionally the EMG Interface, which reads muscle activation even when the limb barely moves — important early after stroke, when intent exists but strength does not.

The controller's policy is assist-as-needed: if the patient drives the movement, the robot fades to near-transparency; if the patient stalls, stiffness ramps up and the robot completes the repetition. Keeping the patient's own effort maximal is what separates therapy from passive motion. On the Control Console, exercises are framed as games on the patient-facing LCD Panel — reaching tasks, tracking tasks — because engagement measurably improves dose compliance, while the therapist's screen shows live force and range data and the Compute SoC Module logs every session for outcome tracking.

Patient interface

Coupling forces into a paretic limb safely is a design problem of its own. The Upper-Arm Cuff and Forearm Cuff are moulded shells with breakaway latches, padded by washable antimicrobial Cuff Liners swapped between patients. The Hand Grip comes in several diameters because grip ability varies enormously across patients. Setup time matters clinically — straps, telescoping links, and the powered Base Column (a Ball Screw lift over a 400 mm range, for seated or wheelchair patients) target under five minutes from transfer to first repetition.

Safety

The robot is a medical device under IEC 80601-2-78, and its Safety System assumes the software will eventually misbehave. A separate Watchdog Board cross-checks joint speeds and torques against fixed envelopes and trips the motor Relay contactors independently of the main controller. Spring-applied Fail-Safe Brakes catch each joint softly on any power loss rather than letting the arm fall. Therapist and patient each hold an Emergency Stop — the patient's is a deadman grip. Below all of it sit the mechanical Range-of-Motion Stops, set by the therapist to the patient's safe range of motion: hard stops that no electrical fault can move past.