Mechatronic device for active rehabilitation of upper limbs

Abstract

Patients may experience difficulties in moving their joints after extensive surgery.

As a result, tissue around the joint will stiffen and scar tissue will form. Therefore

lengthy physical therapy would be necessary for rehabilitation. Continuous Passive

Motion (CPM) is a therapy method designed to aid in the recovery of joints after

surgery. CPM is achieved using motorised device to move the joint constantly. CPM

machine will move the patient‟s forearm about the elbow joint through a defined

range of motion for an extended period of time in order to help the patient regain his

range of motion. However, this method of compensating for lack of ability of the

patient to move his limbs has it flaws. The current technologies of CPM machines do

not require any effort from the user to participate actively during the rehabilitation

exercise. As time passes, the patient may lack motivation in the rehabilitation which

will hinder further recovery.

Therefore Electromyography (EMG) is introduced in this project. EMG is a

method to evaluate and record the electrical activity produced by muscles. The activation

of the exerciser would be based on the EMG signals of the user‟s muscles.

When the user flexes or extends his arm, EMG signals are acquired by an EMG system.

Once the signals detected exceed his threshold, which is pre-set based on his

Maximum Voluntary Contractions (MVC), a program built using LabVIEW will

trigger a motor and activate an exerciser to assist him with the flexion or extension

motion. This type of rehabilitation is suitable to be used by the patients at any point

of time. It helps to motivate the patients to be independent and involve the patient

more in the rehabilitation.

The author designed and implemented a compact, portable, and modular

mechatronic device that can be used for wrist and elbow rehabilitation. A single actuator

is used, and various types of wrist and elbow exercises can also be executed by

adjusting a knob on the device. Besides that, the author also tried out the device on

healthy patients. From the experiments, the author discovered that different type of

person will give different initial EMG values and Maximum Voluntary Contraction

(MVC) values. Therefore, the therapist needs to set different the maximum threshold

value for different patients.