Editorial Feature

Robots and Patient Rehabilitation

Rehabilitation robotics is a branch of robotics that focuses on the development of machines that help people recover from severe physical trauma. Robots designed be multi-functional manipulators to help move material are key to serving as devices to help people with disabilities.

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 as 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, others devices help strength development of these motor movements.

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

Research on robot-mediated therapy for 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 in an active assisted mode, where the movement and target position can be visualized by the patient.

The device was tested for its motion in a three-dimentional workspace to better understand this system to work as rehabilitation technology for the movement of limbs and mother muscle groups.

Individuals suffering from chronic 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 proportional integral derivative (PID) controller.

Erol D et al (2007) designed a rehabilitation robotic system that consists of a low-level controller for providing assistance to 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 completixty of a patient's disability is major design challenge.

To overcome this challenge, an automated rehabilitation system accommodates a high-level controller in conjunction with the 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 cannot 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 continue until the completion of therapy.

Advantages of Rehabilitation Robot

The major advantages of a rehabilitation robot as discussed by Robertson JVG et al (2010) include the following:

  • It can produce repetitive, high quality movements.
  • Man-machine interaction for measuring the progress of a patient.
  • It can record performance-related information.
  • Precise quantification of movement-related parameters.
  • It can provide specific feedback to the patients to enhance their movements.

Products on the Market – Advancements

Some of the advanced products of 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 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 demonstratoion of how this arm can stimulate the different movements and varying speeds to a human arm. The arm is built with torque and absolute position sensors.

Humanoid Robotic Arm2 by Elumotion

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, patented TorqueSwitch™ mechanism for distributing grasp forces, back-drivable palm-spread transmission, servo motors, and high-level CPU command interpreter.

The system allows rapid, low-level access to sensor signals and actuator commands. It has two control modes, Real time 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 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:

Video courtesy of Barrett Technology Inc.

The following are the advantages of WAM™ Arm:

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

Sources and Further Reading

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