Final Design

The final design for the robotic brusher is a motor driven belt and pulley system with brushes mounted to the belt.

The choice for this design was driven by the functional requirements for constant unidirectional brushing, which can be accomplished by attaching multiple brushes to the belt. The other functional requirements of a brushing speed of 3 cm/s and 30 cm/s dictated the choice for the motor and pulleys. The brushing distance requirement of 12 cm dictated the choice for the length of the belt and the overall shape of the frame. Finally, the requirement of 0.3-0.4 N of force required the design of an adjustable arm support to position individual patients' arms.

A cutaway of the brusher showing the pulleys, belts, and brushes, within the framing is shown below.

The hexagonal design was chosen to reduce the speeds at which the brushes rotated around the individual pulleys by reducing the angles of change compared to a two pulley design. The motor used is a NEMA 23 stepper motor, driven by an Arduino connected to a corresponding NEMA 23 motor driver. The motor requires 24 volt power, which is supplied through a universal power supply that is connected to a wall outlet. The stepper motor was chosen to overcome considerable friction in the system at 3 cm/s while also being able to reach the required rpm to move the brushes at 30 cm/s.

Below is a picture of the assembly with the casing constructed for the brusher subassembly, as well as the arm support subassembly.

The main purpose of the casing is to increase the safety of the device. The movement of the belts and pulleys, especially at the high speeds, presents a real hazard if hair or fingers were to get caught. Therefore, the casing is designed to decrease the interaction of the patient with the moving components of the system, with only an opening at the bottom for the brushes to pass through.

The arm support subassembly was designed as a result of the need to brush at 0.3 - 0.4 N and as a result of the design of the brushing subsystem. The way that the brushing subsystem is designed makes it unable to adjust the force of the brushes, as compared to other robotic brusher designs, therefore, it is necessary to adjust the position of the patient's arm in order to still achieve the required force. The arm support has 2 degrees of freedom, one vertical adjustment using the lab jack, and one angular adjustment with a screw to get the patient's arm horizontal and at the correct height.