Industrial Robot Electrical Design: Difference between revisions

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[[Category: Industrial Robot]]
#REDIRECT [[Industrial Robot Development]]
 
=Solenoid Driver=
 
The function of the solenoid driver is to power on and off the solenoid valves. The solenoid driver receives a pulse width modulation signal from the microcontroller and amplifies that signal; the amplified signal is a DC output that energizes the solenoid valve.
 
Possibility is the PWM Driver 1.1 from RepRap wiki [http://reprap.org/wiki/PWM_Driver_1_1?sortcol=0&table=1&up=1 PWM Driver 1.1]
 
=Stepper Motor Driver=
 
The function of the stepper motor driver is to power the stepper motors in discrete increments; the stepper motor shaft then rotates based on how much energy was provided by the stepper motor driver.
 
More information on stepper motor controllers can be found in the following link; the design contained in that link is the one planned to be used for the industrial robot. [[Stepper Motor Controller]]
 
Off-the-Shelf options include [http://www.sparkfun.com/products/10267 EasyDriver on sparkfun] and [http://www.pololu.com/catalog/product/1201 A4983 Stepper Motor Driver on pololu]
 
=Shaft Encoder=
 
[http://mechatronics.mech.northwestern.edu/design_ref/sensors/encoders.html Mechatronics on Digital Encoders]
 
[http://en.wikipedia.org/wiki/Rotary_encoder Wikipedia on Rotary Encoders]
 
The function of the shaft encoder is to determine the position of a motor shaft as time passes. This function is necessary for the industrial robot to perform tasks with accuracy, because the robot's movement is determined not only by the power supplied to the motors but also the load being moved. For instance, more power is required to lift a boulder than a baseball. It is easier, more practical, and more accurate to have a position sensor (shaft encoder) than having to calculate different power inputs for each load.
 
An absolute encoder can identify different positions of the measured shaft, but is more complex than an incremental encoder. However, an incremental encoder only provides relative position information. An incremental encoder can be used as an "absolute" one by saving the relative movement information; for instance, for day 1, joint A moves 5 degrees clockwise from the home position, then day 2, joint A moves 10 more degrees clockwise; by saving the information from day 1, the microcontroller can understand that joint A has moved a total of 15 degrees clockwise from the home position, not just 10 degrees.
 
[http://translate.google.com/translate?js=y&prev=_t&hl=en&ie=UTF-8&layout=1&eotf=1&u=http://sites.google.com/site/proyectosroboticos/encoder Resource for Incremental Encoder Design]
 
[http://www.societyofrobots.com/sensors_encoder.shtml Society of Robots on Incremental Encoder Design]
 
The current development plan is to use incremental encoders for their low cost, high resolution, and simplicity of design and fabrication relative to absolute encoders.
 
Incremental encoders can be split into 2 types: magnetic and optical. The current plan is to use optical encoders.
 
A phototransistor pair can be found here [http://parts.digikey.com/ca/1/43466-opto-sensor-dual-pkg-slot-type-ee-sx1031.html Digikey PT pair]
 
Combining that with schmidt trigger'd comparators, 2 digital outputs can carry signals to the microcontroller, one output to determine direction of shaft rotation and the other output to determine speed of shaft rotation. (if output B changes when output A is high, the shaft is rotating in one direction; if output B changes when output A is low, the shaft is rotating in the other direction).
 
[http://thedenneys.org/pub/robot/encoders/ Denneys on optical incremental encoders]

Revision as of 07:12, 20 July 2011

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