1. 2 DOF Upper Limb Exoskeleton Trainer for Elderly People
Jere Lethtinen
Nimish Bhatt
Niko Räsänen
Samu Salerto
Tuomas Tervamäki

2. Arm exercises
Most of you must be familiar with these exercise machines. Our topic of presentation is related to exercise and muscle strength.

3. Muscle Rehabilitation
Aim
Effects/Causes
Muscle Degeneration
Range of motion
Ageing Effects
Sedentary Lifestyle
Muscle Rehabilitation
Explain: Muscle degeneration
It is accelerated by ageing as you grow older and sedentarty life style i.e. lack of physical activity.
These effects also lead to reduced range of motion
Hence muscle rehabilitation is needed especially in aged population.

4. Exoskeleton :Why? Range of motion (ROM) Adjustable to user Portability
Suitable for elderly people
Complete range of motion helps restore lost range of motion.
Suitable for users varying in age and sex.
Portability allows it to be transported to disabled patients in remote places.
It could be designed to suit elderly people.

5. Muscle contraction: Isokinetic
Constant velocity movement
Varying resistance
Maximal loading throughout entire ROM
Safest form of exercise
Max. Torque:
There are various muscle contractions like isotonic, isometric and isokinetic. Isokinetic exercise consists of,
Constant velocity movement of limbs accompanied by,
Varying resistance such that,
The muscles are loaded maximally throughout the ROM.
Varying resistance ensures that the resistance doesn’t exceed muscle strength hence making it the safest form of exercise.
From research studies, we found torque values of… for shoulder and … for elbow.
Shoulder
Elbow
~14Nm1
~10Nm1
1 Danneskiold‐Samsøe, Bente, et al. "Isokinetic and isometric muscle strength in a healthy population with special reference to age and gender." Acta physiologica 197.s673 (2009): 1-68.

6. Constant velocity & Torque measurement Resistance
Mechanical
Links
Lets consider the elbow flexion movement.
The Exoskeleton would consist of mechanical links connected,
at joints to create resistance to the motion,
Such that velocity stays constant,
Which would require velocity measurement and finally torque measurement to evaluate muscle performance.
Constant velocity & Torque measurement
Resistance

7. Components & Materials
D.C. geared motors (8Nm): Resistance
Rotary encoders: Velocity measurement
Teensy microcontroller: PID Control
Current Sensors: Torque measurement
Aluminium: Lightweight frame
We considered pneumatic, hydraulic and electric actuators, and realised that electric would be the easiest to control but at the same time would be heavier compared to pneumatic.
Motors were coupled to rotary optical encoders for velocity measurement.
Teensy is Arduino based microcontroller with a smaller form factor and had enough output pins to serve our purpose.
Current sensors to measure motor current and derive motor torque.

8. Prototype: 2 DOFs Exoskeleton
Motor: Shoulder joint
Adjustable Frame: Aluminium
Electronics: Control system
The frame is strapped using a vest to the body.
Both the motors are connected to rotary optical encoders.
Electronics includes microcontroller, motor driver, current sensors and bluetooth serial for sending torque and velocity data.
It is powered by and external power supply.
The mechanical movements of device are limited to range of motion so that it doesn’t cause injury.
There is a kill switch which cuts off the mail power to the device as safety is case of malfunction.
Motor: Elbow joint

9. Operation flow chart
The PID algorithm implemented in the microcontroller has a set reference velocity.
When a user applies force, causing movement and rotation of dc motors, the microcontroller detects the movement and also calculates the velocity from encoder, and in turn generated a PWM to drive the motor such that the velocity stays constant.
Once user stops moving his/her arm, the microcontroller switches off the motors.
Both elbow and shoulder motors operate independently on the same flow chart.

10. Scope for improvements
Weight
Ergonomics
Mechanical
Electronics

11. Conclusions Positive user feedback Proof of concept
Foundation for further development