Derek: 2007 07 16

Progress Update

Robotic Arm

1. We had initially wanted to increase the speed of the arm by i) using a gear box & ii) changing the motor to a lower voltage motor. However, option (i) failed to work as the increase in speed led to a reduction in torque which prevented the lead screw to rotate. Also, option (ii) did not really worked as planned.

2. Finally, we decided to increase the speed by changing the lead screw system with a pulley system. The pulley system can increase the speed considerably. This is given by v = r w, where v is the linear speed we are trying to achieve, r is the radius of the pulley and w the angular speed of the motor. To reach the speed of about 10 - 15 cm per sec, and with the current angular speed of 272 rpm, we calculated the radius to be around 5 mm. Also, the amount of torque required to drive the pulley would be equivalent to the frictional force from the pulley. This can be reduced by using bearings and pulley. This is achievable.

3. Finally, we proceeded to restructure the robotic arm. this took about 1 week and the pulley system is tested and is working properly. However, the speed of the arm now is too fast and we would need to reduce the speed (done easily by changing the timer value in the PIC). This is to prevent any recoil from the arm when it hits the end of the axis.

4. Further work is to be done on the z arm. This is because the z arm cannot be replaced to the pulley system. We will still be using the gearbox but at a smaller up ratio. This was tested and is working. We have approached the lab officer in the ECE workshop to help us make a coupling to connect the gearbox to the lead screw.

5. The arm should be completed, hopefully, by tomorrow.

Integration of the arm with the human avatar and virtual terrain

1. Work had been done previously to integrate the arm with the human avatar and virtual terrain. To work on integration with human avatar first to match the speed of the human avatar with the arm.

Backup list

1. Most of the components for the backup list have arrived and will proceed to solder on the extra slaves and masters for testing after the full system is up and running. Should be ready by the end of the month.

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