Difference between revisions of "Msc2G7:Expert3"

Revision as of 15:34, 25 March 2015

Motors & Sensors

25/3 Adapt servos

11/3 Type of Motor Decisions

Based on some requirements for the motor, the decision was made to use a Servo Motor, instead of a Stepper Motor or a DC Motor.

The requirements were the following:

1. The position controllability of the axle of the motor
2. A high power/weight ratio
3. High accurately placed at a desired angle of the axle
4. Being able to stall for some time
5. Being low cost
6. Availability of using a battery to power the motor

In the next 2 documents the decision of the Servo Motor is being explained further

[1]

[2]

5/3 Arduino testing

Attempt to connect and control dynamixel 12a+

Dynamixel control module/chip sn74ls241

4/3 Drive

The most influential decision for the design of the joint is the way the joint is driven. In this document we argue the different drive and the best suitable on for our design needs.

Criteria for the drive

1. Handle high torques/forces (or high speed with a gearbox)
2. Power/weight ratio
3. Accurately controllable
4. Size
5. Sharing energy
6. Maintaining position
7. (Degrees of freedom (+/- 180°) (actually possible for every drive))
8. Accessible for testing

The 4 Differtent Drives

Mechanical

Powerfull, but not sustainable and sharing energy enhances the risk of explosions.

Hydraulic

Unlimited torque, but efficiency starts at high weight. Also extra weigth of the fluids.

Pneumatic

Good power/weight ratio, but low forces and hard to share energy.

Electrical (Best suitable for our design)

The most suitable option. Powerfull and light.

http://www.designnews.com/document.asp?doc_id=230452 http://en.wikipedia.org/wiki/Power-to-weight_ratio http://www.rcheliwiki.com/Power_to_weight_ratio http://www.inmoco.co.uk/electro-mechanical_vs_pneumatic_actuators