RMT PROJECT

Cerebral Palsy (CP) is the most common motor disability among children. The disorder develops when a child experiences neurological damage during the prenatal, perinatal, or early postnatal periods. As a result, children with CP often have significant sensorimotor impairments, specifically in the upper extremities. Rehabilitation strategies with the strongest clinical evidence for restoration of upper extremity motor function include Constraint Induced Movement Therapy and Hand-Arm Bimanual Training. But, these options may be better suited for individuals with mild to moderate levels of impairment and may not be applicable for more severely impaired children. For children with more severe levels of upper limb impairment, mirror therapy could be a more feasible approach. Conventional mirror therapy consists of covering the impaired hand while the unimpaired hand performs exercises in front of a mirror. However, this limits sensory feedback to the user while simultaneously failing to provide a realistic training scenario that mimics movements used during everyday activities. The use of robotics combined with mirror therapy could potentially enhance the effects of traditional mirror therapy as robotic devices can be used to provide haptic feedback to the user. To explore this concept, this current work presents the design of a bilateral haptic robot with flexion / extension of the elbow joint. Here, measured movement of one limb connected to a sensorized gantry enclosed timing belt controls movement of a timing belt linear actuator connected to the other limb. Future work will evaluate the feasibility of this approach in children with CP.

Summer 2023 Oscar Celebration Video Transcript
July 31, 2023
Mentor: Dr. Quentin Sanders
OSCAR Student: Karmel Webster

INTRODUCTION AUDIO:
The focus of my research project for this Summer was to develop a rehabilitation robotic device specifically for the upper extremities for children with Cerebral Palsy. According to the Center for Disease Control, Cerebral Palsy is the most common motor disability in children today. CP develops after a child has experienced brain damage while in the womb or shortly after birth, which results in a decreased range of motion as well as sporadic movements of either the upper and/or lower extremities. Other rehabilitation strategies have been utilized to treat children with CP (such as Constraint-Induced Therapy), but due to there being limited treatment options and a need for more devices that treat severe cases of CP, additional rehabilitation methods have been explored, such as conventional mirror therapy.
Conventional mirror therapy works by covering the affected hand, while the unaffected hand remains uncovered to perform exercises in a mirror.
but the downside of conventional mirror therapy is that it only provides visual feedback and lacks sensory feedback, which limits the therapeutic benefit while simultaneously failing to provide an accurate training scenario that mimics movements used during everyday activities.
As a result, the objective of this research project was to develop a bilateral haptic robot that employs the concept of traditional mirror therapy by providing both visual and sensory feedback through execution of flexion and extension movements of the elbow.

CONTROLS AUDIO:
In order to develop this device, my mentor, Dr. Sanders, first taught me about the controls needed for this robot ,which first focused on using a Potentiometer (which is a variable resistor, that produces an output value from 0-1023) in order to control the position of a DC/direct current motor.
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Over the course of the Summer, I learned that PID control is a commonly used feedback loop system which stands for Proportional, Integral and Derivative. The proportional term is calculated by multiply the proportional constant (kp) by the error term, and is therefore directly responsible for decreasing the error in the calculated control signal, while the integral and derivative terms are calculated using the finite difference theorem (which is shown in the picture) in order to smooth out the control signal.
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The constants Kp,Ki, and Kd dictate how much each term will be represented when the control signal is calculated.
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Ultimately, I learned that PID controls the position of a motor by measuring the original position of the motor (using the encoders on the motor), and subtracting this value from the target position (which is the position of the potentiometer) in order to calculate the error term.
Once the error term was calculated, it was sent to the controller (which was the Arduino Uno) in order to be converted into a control signal that ultimately traveled to the plant (which is the DC Motor).
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This will turn the motor shaft clockwise or counter clockwise, which is dictated by the control signal and is displayed here in the video:
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learning this information allowed for the robot to be controlled using a DC motor, an Arduino mega, and a rotary encoder (instead of a potentiometer).
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DESIGN:
The next part of this project focused on the design aspects needed for the elbow module of the robot, which is displayed here in the design sketch along with the name of each component. The elbow module of the robot contains a motorized side (right side) and a sensorized side (left side), due to containing a motor and rotary encoder. In regard to the functionality of this robot, as the patient moves the rotary cart hand platform on the sensorized side, the hand cart will move the timing belt along 2 linear shafts. As the timing belt moves, it will simultaneously move the small metal pulley attached to the rotary encoder shaft, ultimately changing its position. This position change will then travel to the microcontroller (an Arduino mega), which will then convey a control signal message to the DC motor. When the control signal reaches the motor, the patient’s hand located on the right platform (which is the motorized side), will move in response to the position change from the rotary encoder.
—————————————————————————————————————————————— While some robot parts were purchased, I learned how to use the Cading Software called Fusion 360 in order to build 3D support models needed for the robot. This included:
A large 3D mount used to hold one side of the pulley and timing belt in place, which is show here in picture from the sketch diagram, as well as the CAD model and the printed 3D model.
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Smaller 3D mounts used to hold the long linear shafts in place.
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The hand clip, hand rotary cart, and hand platform for the patient to grab onto and push in order to move the timing belt along the linear shafts.
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A motor stand and rotary encoder stand to support and prevent excessive movement of the motor and encoder, while also securing the second pulleys on the opposite sides of the timing belt.
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Here is a picture of the right side of the robot (which is the motorized side of the robot). The left side of this robot (which is the sensorized side), is still being developed.
CONCLUSION:
Though the motorized side for this device has been developed, and the development of the sensorized side is still underway, we plan to implement pronation/supination movements to this robot for wrist movement, as well as a grasping motion to the robot for the patient’s hands.

Thank you!