Editorial Feature

Robots and Patient Rehabilitation

This article was updated on the 3rd September 2019.

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Rehabilitation is an important phase of a patient’s treatment. Usually, rehabilitation occurs when the patient has suffered from illness or severe physical trauma, affecting the nerves and musculoskeletal system.

There are various rehabilitation treatments, including physical therapy, occupational therapy, and physiotherapy, to name a few. Recently, thanks to technological advancement, rehabilitation robotics has been established.

What is rehabilitation robotics?

Rehabilitation robotics is a branch of robotics that focuses on the development of machines that help people recover from severe physical trauma. Robots designed to be multi-functional manipulators can help during the rehabilitation phase of patients recovering from injuries.

Rehabilitation robotics have been found to be effective in people suffering from motor impairments due to stroke. Since its evolution in the 1960s, rehabilitation robotics has been developed through assistive devices, orthotics, prosthetics, and robot-mediated therapy. This assistive technology aims to enhance the efficacy of medical therapy and to increase the ease of activities performed by patients with disabilities.

Robotic devices are currently being used as exoskeletons such as the Myomo neuro-robotic system and Tibion bionic leg for helping hand or limb movement, and robotic arms such as MIT-MANUS. While certain devices aid specific motor movements directly, other devices help strength development for these motor movements.

Robotic technologies designed to increase the intensity and repetition of a task for aiding in the enhancement of movement are used to help support neuroplasticity in the rehabilitation of patients with disabilities.

Research on robot-mediated therapy for the rehabilitation of patients suffering from stroke has increased significantly, owing to its inexpensiveness and effectiveness.

Design of Rehabilitation Robot

The first robotic assistive device, MIT Manus, employs an impedance controller for assisting the movement of the patient’s arm to the target location. It is used in an active assisted mode, where the movement and target position can be visualized by the patient.

The device was tested in a three-dimensional workspace to better understand this system in its aim to work as a rehabilitation technology for the movement of limbs and mother muscle groups. Individuals suffering from stroke can be treated using the mirror image movement enabler (MIME) and the assisted rehabilitation and measurement (ARM) guide.

MIME uses a manipulator that works by moving a patient's arm with the help of a pre-programmed position trajectory using a proportional integral derivative (PID) controller. Erol et al (2007) designed a rehabilitation robotic system that consists of a low-level controller for aiding the patient's arm movement.

As with any technology, faults in automated systems can hinder the successful completion of tasks. Combining faults in a robot's motor joint with a need for performing more challenging tasks based on the complexity of a patient's disability is a major design challenge.

To overcome this challenge, an automated rehabilitation system accommodates a high-level controller in conjunction with a low-level controller for monitoring the task and safety of the patient. It also provides task updates to the low-level controller.

However, the high-level and low-level controllers can’t directly communicate with each other as they require different types of inputs and outputs. Hence, the system also includes an interface that converts continuous-time signals into sequences of discrete values and vice versa.

A process-monitoring module monitors the state information of robot and patient via the interface to trigger the corresponding events that are represented through plant symbols. A decision-making module of the high-level controller forms sequences of control actions by using decision rules when the controller receives the event. The decision is sent to the low-level controller via the interface by using the control symbols.

The interface then transforms the control symbols into the plant inputs that are used for updating the task. Finally, the updated task is controlled by the low-level controller. This cycle continues until the completion of therapy.

Advantages of Rehabilitation Robot

Rehabilitation robotics can help many patients across the globe. At the same time, it can help patients with limited mobility due to trauma or stroke to move around.

The other major advantages of rehabilitation robots include producing repetitive and high-quality movements, having precise quantification of movement-related parameters, providing specific feedback to the patients allowing them to enhance their movements, recoding performance-related information, and providing man-machine interaction to measure a patient’s progress.

Products on the Market – Advancements

Some of the advanced products in rehabilitation robotics currently available on the market include the following:

Elu2-Arm

Elumotion's Elu2-Arm is specifically designed for supporting human-robot cooperation. It can be configured as a left or right arm.

It features a CANbus motor controller, limit/homing switches, torque sensor, absolute position sensor, and incremental position sensor. The CANbus motor controller can operate the joints and monitor the sensors.

The following are the anatomical movements simulated by the joints of the robot arm:

  • Wrist flexion - extension
  • Wrist adduction - abduction
  • Wrist pronation - supination
  • Elbow flexion - extension
  • Humeral - rotation
  • Shoulder adduction - abduction
  • Shoulder flexion - extension

The video below is a demonstration of how this arm can stimulate the different movements and varying speeds associated with a human arm. The arm is built with torque and absolute position sensors.

BarrettHandTM

The BarrettHandTM developed by Barrett Technology Inc is a self-contained, low profile robotic hand that can be used for grasping applications.

This technology features patented reconfigurable spreading fingers, the patented TorqueSwitch™ mechanism for distributing grasp forces, a back-drivable palm-spread transmission, servo motors, and a high-level CPU command interpreter.

The system allows rapid, low-level access to sensor signals and actuator commands. It has two control modes, RealTime mode, and supervisory mode. It can firmly grasp objects even on precision and delicate surfaces.

The key benefits of BarrettHandTM include the following:

  • Lightweight
  • High-speed communications
  • Minimizes signal noise and torque on the robot's wrist
  • Quick/simple arm attachment
  • Flexible automation
  • Improved throughput in pick-and-place applications
  • High programming flexibility
  • Convenient testing platform.

WAM™ Arm

Another robotic arm developed by Barrett Technology Inc is the WAM™ Arm that has a direct-drive capability which is supported by Transparent Dynamics™ between the joints and motors. It features a back-drivable manipulator and is available in two main configurations, 4 and 7 degrees of freedom. This joint range exceeds that of other conventional robotic arms. Bill Townsend, CEO of Barrett Technology Inc. introduces the WAM Arm in the following video:

The following are the advantages of WAM™ Arm:

  • High dexterity
  • Robust
  • Extremely small, weighing only 43 g
  • Power-efficient.

MIT-Manus

MIT-Manus is a new robot undergoing clinical tests. It provides shoulder and elbow training. The clinical trials have shown that the robot-aided neurorehabilitation is effective in reducing impairment during stroke recovery.

The system requires the patient to hold or grip a robotic joystick that chaperons the patient’s arm, hand, or wrist while performing certain movements. The technology will assist the brain in making new connections. Hence, it will help the patient to re-learn movement in a limb on his or her own.

Sources and Further Reading

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