Design+Challenge

Mr. Happer's file about Design Challenges -->

This design challenge was to make a robotic arm out of a kit. Following the instructions in the included instructions book, we wired motors, put in a few gears, and stuffed it in a plastic shell. And we were done.
 * a statement of the design challenge**


 * evidence of the performance of your design as well as a detailed, labeled sketch of how it was constructed**

Animation The .swf file can't be uploaded- I've given up. So here is a frame by frame display... in comic book form.



Video media type="custom" key="4930507"

power(ch 6): The time rate of doing work: power=workxtime. Our robotic arm can do work in a set amount of time, therefore it has power. machine (ch 6): A device such as a lever or pulley that increases (or decreases) a force or simply changes the direction of a force. The robotic arm is a machine. work (ch 6): The product of the force and the distance through which the force moves: W=Fd. The robotic arm can exert a force over a set distance, therefore it can do work. watt (ch 6): The unit of power, the joule per second. The power in the robot arm can be measured in watts. efficiency (ch 6): The percentage of the work put into a machine that is converted into useful work output. Because the robotic arm is a machine, it has a measure of efficiency. direct current (ch 9): Electrically charged particles flowing in one direction only. Because the robotic arm runs on batteries, it uses direct current. electric current (ch 9): The flow of electric charge that transports energy from one place to another. Measured in amperes. Electric current flows throughout the arm. parallel circuit (ch 9): An electric circuit in which electrical devices are connected so that the same voltage acts across each one, and any single device completes the circuit independently of all the others. Because the arm uses a parallel circuit, each motor is operated independently of the others. electric motor (ch10): A device employing a current-carrying coil that is forced to rotate in a magnetic field. A motor converts electrical energy to mechanical energy. There are multiple electrical motors in the arm.
 * terms (8-10)**


 * one or more labeled images that explain how the main physics concepts relate to the design. + text to clarify**

__Direct Current__ Rotational direction in a motor is changed by reversing the polarity of the direct current. In this machine, batteries are oriented in opposite directions. The motors connect to either system by a switch. In Figure 14, the switch is not connected to either of the battery systems. The motor does not turn. In Figure 15, the switch connects to battery terminal A, a positive terminal. The current flows counterclockwise. In Figure 16, the switch connects to battery terminal B, a negative terminal. The current flows clockwise.

__Force/Torque__ The torque of the motors in this machine has only a few g/cm, which is not enough to move the weight of the main body. To achieve enough force to drive the joints, gears are needed. Gears increase torque by reducing rotational speed. Rotational speed and torque are inversely proportional. The bigger the gear, the less rotational speed. Therefore, bigger gears produce more torque.


 * A brief reflection on the design process**

The design process was easier than expected. The textbook was fairly easy to understand and the parts usually fit together. The most difficult part was wiring it together.

The terminals were hard to assemble. They seemed to be too small to fit over the flanges. After struggling for almost an entire class period, Mr. Happer pointed out that we had to use pliers. This helped a lot.


 * Citations**

Hewitt, Paul G., et al. //Conceptual Intergrated Science Explorations//. San Franscisco: Addison-Wesley- Pearson, n.d. Print. OWI. //Movit Robotic Arm Trainer: Textbook of Robotic Arm Trainer//. Carson: EK Japan, 1998. Print.