Introduction
InProblem Statement
We seek to enable motor-impaired students in Julie Cimino’s art class , one of her physically-disabled students has little to no control over the actions of her limbs. As a result, she uses a wheelchair and has some ability to rock her upper body back and forth. Traditional art equipment is difficult to use, so we are setting out to build a sketching mechanism that she can interact with.
The basic black box model
to engage in projects by creating an accessible sketching mechanism.
Concept
The function model to the right outlines the context of the mechanism's use. As shown on the right, motion detected by the
plan is to use accelerometer data from her movementaccelerometer is used to actuate a
signalmotor that drives
a “sketching robot mechanism”. The use of the accelerometer provides a causality link between her actions and the output sketch which is important to making the mechanism engaging for the user.
our sketching mechanism. This method allows the user to feel engaged in the process as their motion, detected by the accelerometer, causes the mechanism to operate.
The red box denotes the kinematics challenge we are attempting to solve.
The initial mechanism design concept is shown to the left. The outer and inner radii of the cam map to the desired x and y positions of the output joint, respectively. The motion of the output joint is then magnified using a pantograph mechanism shown at the top of the sketch. A pencil or pen is at the mechanism's end effector in order to draw the output path.
The cam will be actuated rotated with constant angular velocity, ω, to avoid introducing jerky motion. To implement this, the DC motor and encoder will be implemented using a proportional controller will be used in the control system to maintain velocity even with changing torque loads on the motor.