Msc2G7:Expert3

Motors & Sensors

BOP

Weekly Planning

Joints&Calculations

Motors&Sensors

Control

Plenary Session 2

Questions

Servo testing

Servo testing 250gr on 30cm arm. Testing the power demand.
http://re.hyperbody.nl/pdf/Film1.2.mp4
Servo testing 250gr on 40cm arm.
http://re.hyperbody.nl/pdf/Film2_2.mp4

6/5 computer, sensor and connection choices

1. One joint with sensor working
Raspberry pi/Arduino control motor with sensor

2. Two (Micro)Computers Communicating ethernet/bluetooth

3. Advanced control Consensus Algorithm

25/3 Adapt servos

The brown wired element on the right is the potentio meter. That measures the angle of the output axle of the motor. The turning angle of the meter is limited to less than 360 degrees. So that causes a problem when putting any gears on that axle to increase torque. The meter has to be replaced to the good axle of the right measurements.

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

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With the support of the Culture Programme of the EU.