1 Introduction
2 Human Gait Analysis
2.1 Anatomy of Lower Limbs
Part/joint | Degree of freedom | ROM (m; degree) |
---|---|---|
Pelvis | Superior/inferior | 0.1/0.1 |
Lateral | 0.15/0.15 | |
Anterior/posterior | 0.2/0.2 | |
Obliquity | 10/10 | |
Tilt | 6/6 | |
Vertical rotation | 15/15 | |
Hip | Flexion/extension | 40/30 |
Adduction/abduction | 20/20 | |
Internal/external rotation | 15/15 | |
Knee | Flexion/extension | 75/0 |
Ankle | Dorsiflexion/plantarflexion | 25/35 |
Adduction/abduction | 10/10 | |
Internal/external rotation | 10/20 |
2.2 Analysis on Human Gait
3 Mechanics of Lower Limb Rehabilitation Exoskeleton Robots
Human | Treadmill-based exoskeletons | Overground exoskeletons | ||||||||
---|---|---|---|---|---|---|---|---|---|---|
Part/joint | Degree of freedom | Lokomat | LOPES | ALEX III | eLEGS | Indergo | Rewalk | Rex | Mindwalker | HAL |
Pelvis | Superior/inferior | Passive | Passive | Passive | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ |
Lateral | Passive | Actuated | Passive | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | |
Anterior/posterior | Passive | ‒ | Passive | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | |
Obliquity | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | |
Tilt | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | |
Vertical rotation | Passive | ‒ | Passive | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | |
Hip | Flexion/extension | Actuated | Actuated | Actuated | Actuated | Actuated | Actuated | Actuated | Actuated | Actuated |
Adduction/abduction | ‒ | Actuated | Actuated | Passive | Passive | Passive | Passive | Passive | ‒ | |
Internal/external rotation | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | Passive | ‒ | ‒ | |
Knee | Flexion/extension | Actuated | Actuated | Actuated | Actuated | Actuated | Actuated | Actuated | Actuated | Actuated |
Ankle | Dorsiflexion/plantarflexion | Passive | ‒ | Actuated | Passive | Passive | Passive | Actuated | Passive | Passive |
Adduction/abduction | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | Passive | ‒ | ‒ | |
Internal/external rotation | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | ‒ | |
Actuation | ‒ | Electric | Cable-driven SEA | Electric | Electric | Electric | Electric | SEA | Electric | Electric |
3.1 Anatomy of Human Upper Limbs
3.2 Actuation Design
4 Control of Lower Limb Rehabilitation Robots
4.1 Trajectory Planning
4.2 Control System
Control strategies | Method | Devices | Features |
---|---|---|---|
Position control | Finite state machine | eLEGS, Indergo | A finite state machine is used to indicate the intended option of a series of maneuvers. The user’s intended maneuver is then determined based on the provided inputs. Each state is defined by a set of joint angle trajectories, which are enforced by position control loops |
Trajectory tracking control | Rewalk, Rex, MINDWALKER | After selecting the walk mode based on sensors, the participant initiates and propagates programmed motions like walking, turning, sitting, standing and shuffling. This also enables a person to move using a joystick and remote controller | |
Force controller | Selective control of subtasks | LOPES | Human gait is divided into different subtasks. These subtasks are controlled separately based on the impedance controller |
Impedance control | Lokomat | Torque is supplied by the robot using a PD controller based on the deviation between the actual and desired angular trajectories. Thresholds of maximum allowed deviations are determined around the reference angular trajectory | |
EMG-based control | Virtual torque control | HAL | Human joint torque is estimated based on EMG signals to generate virtual torque for controlling the motors |
Assist-as-needed control | Force field control | ALEX | Tangential and normal forces are applied at the ankle of the subject based on the deviation of the actual path from the desired path |