Robot Arm - minirob


Here is a little bit of information about my small (1.6m high) Robot Arm.

The robot is a simple 6axis Arm rotating upto 270degrees per axis.

The hardware to control the robot is very simple indeed. it consists of 6x h-bridge drivers connected to a PIC16f877 which creates the PWM signal for the motors. It has a simple RS232 interface, and control the robot to +/-2 degrees of accuracy.

This may sound like a fairly adequate amount of accuracy, but it is not. As the inaccuracy in each axis traverses each limb in the arm, the accuracy (error) is ampified. The end effector of the Arm end up in a wildly inaccurate place.

The simple electronics hardware tests the robot structure well, and helped develop a model for the arm.

Current interface design

Hardware Description

The processor is a Microchip PIC16F877A @ 10MHZ.
This chip has 8 A/D channels, and will allow us to read the feedback from the potentiometer on each axis.

porta - h-bridge
portd - max232 pc interface
portb - lcd interface

H-Bridge design

There are two types of h-bridge chip used in the minirob arm. The larger motors are run from the extremely fragile and expensive L6203D h-bridge driver. The smaller ones are
Hardware Interface description

The PC has to send a command to the serial port in the format as such


S = start bit. literal "S" string
1st digit = reserved
digit 2,3,4 = axis to address (0-255)
digit 3,4,5,6 = position is degrees to move to (0 - 1024 range)
digit 7,8,9 = speed to use (0-255)

where each segment is the movement parameter for an axis.

----picture of hardware and software in gallery----

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