Precision Robotics R. M. Satterthwaite R. Shockency Advised By: Dr. B. D. Huggins Mr. C. Mattus

Introduction Our objective is to create a low cost robotic platform capable of precise movements related to user inputs. Our objective is to create a low cost robotic platform capable of precise movements related to user inputs. Provide a basic platform for future projects to start from. Provide a basic platform for future projects to start from.

Outline The Complete System The Complete System Another fabulous drawing by Rob. “Paint Rules!!” Another fabulous drawing by Rob. “Paint Rules!!” Microprocessor Microprocessor The heart and soul The heart and soul Power Electronics Power Electronics H – Bridges, the devil incarnate H – Bridges, the devil incarnate CPLD CPLD The motor reader The motor reader Platform Platform Bringing it all together into one cute package Bringing it all together into one cute package

System Note: Paint is the best Graphics program on The market.

Microcontroller Data Processing Data Processing CPLD interface to reduce work load CPLD interface to reduce work load Performs real time speed, distance, and turning calculations Performs real time speed, distance, and turning calculations Acts as a memory device Acts as a memory device Crude Closed Loop Controller Crude Closed Loop Controller Speed control for 2 motors Speed control for 2 motors Distance control for 2 motors Distance control for 2 motors Turning control for 1 vehicle Turning control for 1 vehicle 500 Hz, 1791 Step Variable PWM 500 Hz, 1791 Step Variable PWM

User Interface Keypad Entry Keypad Entry 2 = Forward 2 = Forward 8 = Backward 8 = Backward 4 = Left 4 = Left 6 = Right 6 = Right E = Enter E = Enter F = Clear F = Clear LCD Menu System LCD Menu System Handles Single Commands Handles Single Commands

User Interface

8 Bit Representation of Motor Speed Used as a Control Variable

01791 FFFF HEXF900 HEXComplement Point 5 Volts 0 Volts Closed Loop Control

The PWM Signal 500 Hz 500 Hz 1791 divisions 1791 divisions.0558% increments of the duty cycle.0558% increments of the duty cycle CRCH, CRCL CRCH, CRCL Sets the PWM Period Sets the PWM Period FFFF-F900 = 6FF (Produces 2 ms interrupt) FFFF-F900 = 6FF (Produces 2 ms interrupt) CCH1, CCL1 CCH1, CCL1 Controls the “Complement Point” of the PWM Controls the “Complement Point” of the PWM The process is backwards because the hardware uses a count overflow to signify the end of the process. The process is backwards because the hardware uses a count overflow to signify the end of the process. FFFF = overflow point FFFF = overflow point FFFF = 0% Duty Cycle FFFF = 0% Duty Cycle F900 = 100% Duty Cycle F900 = 100% Duty Cycle

H-Bridges What are they? What are they? Power Transistor array with logic for direction control and breaking. Power Transistor array with logic for direction control and breaking. Logic ports not very robust Logic ports not very robust Destructive Noise Destructive Noise Power and grounding Power and grounding Noise from motors Noise from motors Noise to encoder wheels Noise to encoder wheels

The H-Bridge Yes, electrons are blue….

Intermission

CPLD Why CPLD? Why CPLD? Speed Speed Non-volatile memory Non-volatile memory Easy diagnostics and testing Easy diagnostics and testing Mass Production Mass Production Two CPLDs Needed Two CPLDs Needed CPLD 1 – Freq Counter/Angle (75% Utilized) CPLD 1 – Freq Counter/Angle (75% Utilized) CPLD 2 – Distance (65% Utilized) CPLD 2 – Distance (65% Utilized)

CPLD - Counter Frequency counter for motors 1 and 2 Frequency counter for motors 1 and 2 Real time calculations of speed for both motors Real time calculations of speed for both motors Refresh rate of 10 Hz Refresh rate of 10 Hz Cascaded counters (8-bit and 4-bit) Cascaded counters (8-bit and 4-bit) First count = 0 to 15 First count = 0 to 15 42,000Hz / 256 = 160, 160 / 10Hz = 16 42,000Hz / 256 = 160, 160 / 10Hz = 16 Two counts, First count and Sum count Two counts, First count and Sum count Check and Sent Check and Sent

CPLD – Distance Distance calculation code Distance calculation code Allows distance count in CM and M Allows distance count in CM and M Max of 256 Meters Max of 256 Meters Increments register for microprocessor Increments register for microprocessor 663 counts per CM 663 counts per CM 500 * 65.5 / 49.4 = or 0.007% error 500 * 65.5 / 49.4 = or 0.007% error 0.67CM error per 100Meters 0.67CM error per 100Meters On CPLD 2, 4 registers, 2 Per Motor On CPLD 2, 4 registers, 2 Per Motor

CPLD - Angle Angle calculation code Angle calculation code Allows angle calculation to 1º Allows angle calculation to 1º 2 Registers, 1: 0º - 179º, 1: 180º increments 2 Registers, 1: 0º - 179º, 1: 180º increments Increments register for microprocessor Increments register for microprocessor At 38.88CM width, 225 counts per degree At 38.88CM width, 225 counts per degree (38.88 * π * ) / 360 = or 0.03% Error (38.88 * π * ) / 360 = or 0.03% Error 0.1º error per 360º 0.1º error per 360º On CPLD 1, 2 Registers, 1 Motor On CPLD 1, 2 Registers, 1 Motor

CPLD - Addressing Interface to the microprocessor code Interface to the microprocessor code 8 registers addressed on 2 CPLDs 8 registers addressed on 2 CPLDs Enable and 4 registers each using 3 address lines Enable and 4 registers each using 3 address lines Tri state buffer on EMAC bus lines Tri state buffer on EMAC bus lines Problems Problems Can’t tri state parallel port pins or microprocessor port pins Can’t tri state parallel port pins or microprocessor port pins Frequency input can not be same pin as clock Frequency input can not be same pin as clock

Platform Cut and milled, then folded and bolted Cut and milled, then folded and bolted Symmetrical for turning Symmetrical for turning Wheels encased for less stress on the motor shafts Wheels encased for less stress on the motor shafts Casters allow for pivot turning Casters allow for pivot turning Bearings – Nylon for casters and drive wheels Bearings – Nylon for casters and drive wheels

Platform Power switch and charging switch in one! Power switch and charging switch in one! Batteries and motors on bottom plate Batteries and motors on bottom plate All electronics on top two tiers All electronics on top two tiers Hardboard for future changes is controlling hardware Hardboard for future changes is controlling hardware Central Disconnects Central Disconnects

Platform

Electronics

Complete System

It’s ALIVE!!

Questions