Walking Robot with Vision. Group 14 Anselet Jacques Phillipe Jean-Jumeau Steven Schultz

Transcription

1 Walking Robot with Vision Group 14 Anselet Jacques Phillipe Jean-Jumeau Steven Schultz

2 Our Mission, Our Purpose We intend to build a six-legged robot that will be able to walk, be controlled wirelessly by a PS2 controller, and has a way of discerning certain colors.

3 Individual Responsibilities Phillipe PS2 Controller and Wireless Communication Anselet & Phillipe Walking Steven Color sensor Anselet Power supply system

4 Leg Dimensions: Knee to Foot = 141 mm Hip Vertical to Knee = 57 mm 3DOF (degree of freedom) It incorporates ball bearings at each joint Made of aluminum alloy We will be using 6 of them

5 Servomotors HS-475HB It has an operating voltage between 4.8 and 6 volts. Capable of 76 oz.-in. of torque Speed: It can cover 60 degrees in 0.18 seconds Has a maximum range of 180 degrees 18 of them (6 per leg) will be necessary

6 Control and Communication: Overview This is a basic block diagram of the control and wireless communication system.

7 Lynxmotion s SSC-32/Servo Controller Lynxmotion s SSC-32 servo controller is used to help in coordinating the servomotors Operates between 6 and 9V Since 32 channels are available, it can coordinate up to 32 servomotors. It is equipped with Atmel s Atmega168-20PU and Microchip s 24LC32P 32KB EEPROM.

8 SSC-32/Servo Controller Both the Atmega168 and the EEPROM are preprogrammed with a firmware. With the free software PowerPod from Lynxmotion, it is configured for the operation of 18 servomotors and the correct initial position of the servomotors. A microcontroller or a computer is needed to stream in the appropriate command data serially at the servo controller s receiver port.

9 PS2 Controller Interpreter We will be using a DualShock2 PS2 Controller. A microcontroller will force it into Analog mode, to enable the use of the two joysticks of the controller. A microcontroller will be programmed to emulate the PS2 console in order to interpret the data from the PS2 Controller for the servo controller.

10 PS2 Controller Interpreter Of the 9 pins of the PS2 controller connector, only 5 of them will be used for our purpose. The communication between the PS2 controller and the MCU is full duplex and serial, and is done through the lines Command and Data. The sampling on each side is synchronized and monitored by using the Clock and Attention lines. 5 is fed through the VCC pin. Then, besides the Ground pin, the rest (Vibration Motor Power and Acknowledge) is ignored.

11 PS2 Controller Interpreter MCU processes the PS2 controller data corresponding to the buttons used and transmits byte-frame serial data wirelessly at a baudrate of For this, we need a microcontroller that has byteframe serial data transmission capability at baud, as the servo controller does. Due to the projected volume of the code, a microcontroller with a sizable Flash/ROM is necessary.

12 PS2 Controller Interpreter This is the flowchart of the subroutine responsible for the communication between the PS2 Controller and the MCU.

13 Microcontroller Microcontroller needed: Of sizable Flash/RAM/ROM due to the projected volume of the code and the incredible amount of constants and variables that will be used in calculations. Has byte-frame serial data transmission capability at a baudrate of bps

14 Microcontroller TI s MSP430F2370 was out of question due to the package type. The Atmega644 and the Atmega644P were chose and experimented with, but ultimately dropped, because the size of their EEPROM was not enough

15 After some research, we stumbled upon BasicMicro s Atom Pro 28 microcontroller It is recommended by robotics enthusiasts. No programmer needed: It can be done by using 4 pins of the chip, an RS232 cable and a PC. Microcontroller It is equipped with 2KB of RAM and 32KB of EEPROM Each of its I/O pins are capable of outputting byte-frame serial data at a set baudrate. Easier to program since it can be programmed in BASIC

16 PS2 Controller Interpreter This is the schematic of the PS2 Interpreter circuit.

17 Wireless Communication Data from the Atom Pro need to be transmitted wirelessly to the servo controller. A transmitter and a receiver are needed. Linx Technologies TXM-916-ES transmitter and RXM-916-ES receiver modules, which operate at 916 MHz, were chosen They are simple plug-and-play devices, fairly easy to use The downside is that a PCB board is a must, even to test it, and they require an antenna to be installed. PCB boards were designed and built for both the transmitter and the receiver. During testing, its performance was not consistent, since they operated correctly only at times.

18 Wireless Communication We turned to the Xbee Modules from Digi. They are definitely more reliable and robust. An antenna is already mounted on each of them. The Xbee protocol 1 mw with wire antenna was chosen Though they are mostly used as transceivers, one will be configured as a transmitter and the other as a receiver. Using Windows Hyper Terminal, they are configured to operate with the highest output power (0 dbm), with a serial interface rate of bps.

19 Vision: Overview LEDs shine white light on to object Colored light reflects off object and into color sensor. Color Sensor converts light intensity into pulses; the higher the light intensity the higher frequency of square pulses Microcontroller counts the number of pulses within a given sample period and determines if met then LIGHT LED, if not, keep searching/counting.

20 Vision: In the beginning Considered FPGA implementation Camera Video decoder No one in group familiar with VHDL or testing/troubleshooting FPGAs big factor. Considered Microcontroller implementation Memory limitations Timing complications Speed limitations Seemed ideal because we could program in a familiar language, C.

21 Vision: Initial Testing and Simulation MatLAB

22 Vision: Reconsideration What we really needed was low-level image/video processing. Our simple task of detecting color blobs would have required us to utilize edge-detection algorithms and histograms relatively simple. But their was a gap in hardware application-specific DSP chips are expensive; microcontrollers are inexpensive yet underpowered. The solution: LIGHT-SENSING CIRCUITS WITH COLOR LIGHT FILTERS.

23 Vision: Background White light contains all colors of the spectrum. Objects of a certain color (i.e., red) absorb all other colors and reflect back that certain color. Photoresistor/LDR Lowers resistance as light intensity incident component increases. Phototransistor Works the same as BJT, but uses light intensity. The electrons that are excited by photons in the base-collector junction are injected into the base, and this photodiode current is amplified by the transistor's current gain β.

24 Vision: First Trials LDR circuit What wouldn t work Ambient room light too strong for circuit. Unreliable color filters unavailable Problems with components Lack of datasheets for parts bought. Nonlinear characteristics of photoresistor and phototransistor made trouble-shooting difficult. After some more research we found a much more viable solution.

25 Vision: Color Sensor Two Options: TAOS TSL230RD and Avago ADJD-S371-QR999. Both convert light to frequency with color filters and photodiode array. Each chip has photodiode array with red filter, green filter and blue filter. The Avago IC gave more control of the input/output (timing considerations included) but for our purposes, we decided on the TSL230RD. The TSL230RD is easier to interface and program for. TAOS TSL 230RD Avago ADJD-S371- QR999.

26 Vision: Color Sensor PICAXE Color Sensor is an assembled TAOS TSL230RD on board with a lens assembly and pin connectors.

27 Vision: Color Sensor PicAXE Color Sensor Schematic Pin # - Use V 2 S3 (Color select) 3 S2 (color select) 4 OUT (to MCU) 5 0 V 6 LED +5V 7. S0 (unused) 8. S1 (unused) 9. OE chip enable V COLOR S3 S2 Red filter 0 0 Blue filter 1 0 Green filter 1 1

28 Vision: Microcontroller Options PICAXE18X is a PIC18 with a preloaded programmer so that the chip is directly programmed. The PICAXE18 also featured the COUNT command to count the pulses. The ATMega644 was too much muscle for our purposes.

29 Vision: PicAXE18X Schematic Used: Input 2 color sensor input Input 1 Set switch Input 7 S3 Input 6 S2 Output 7, 6, 5 Red, Green, Blue LEDs

30 Vision: PicAXE18X Electrical Characteristics

31 Vision: Program Program written in BASIC Inputs: SET, S3, S2, Color sensor. Outputs: Red LED, Green LED, Blue LED. Features a SET switch that works like a pause button. When SET = 0 the program scans the selected color indicated by switches S2 and S3. When SET = 1 the program stops color scanning and allows the user to change color to detect. When program knows what color it is looking for, it goes to the respective subroutine and counts the number of pulses in the sample time sent from the color sensor. When the threshold of pulses within that sample time is met, it blinks the respective LED for that color.

32 Vision: Program

33 Vision: Simulation Program written in BASIC

34 Vision: Overall Schematic

35 Vision: Testing Calibrating Because the PICAXE Color sensor has a lens, it keeps most IR light out and the colored filters allow only the colored light to come through. In the program thldred, thldblu, and thldgre are the threshold values for the samples. Testing for these values was a trial and error process. Detected-object square pulse frequency was anywhwere from 4 khz to 6.2 khz. [6200 Hz * (1 s/1000 ms) * Sample time = # of pulses to break threshold.] Color Red 150 Blue 300 Green 275 Threshold (pulses/sample time)

36 Vision: Shortcomings Range We found the range of the sensor to be quite small. About 1-3 inches. Object surfaces also made a difference. Reflective vs. Non-reflective Threshold values were easily changed, though.

37 Power Supply: Overview Power requirement for the different subsystems of the robot

38 Power Supply: Overview Given that the servos burn the most power, and to keep the electronics; microcontrollers, transmitters and receivers, from malfunctioning because of lack of power, we decided to use two batteries to power the robot. A 6.0 V battery to power the servo-motors A 12 V battery to power the electronics

39 Power Supply: Battery Different Rechargeable battery types We took into consideration the capacity, performance in high drain devices, rechargeable ability and price of the battery

40 Power Supply: Nickel Metal Hydride We chose the Nickel Metal Hydride battery type, because it has A high capacity A high rechargeable ability A high performance in high drain devices, which is ideal for our servos since they draw a lot current. A relatively low price

41 Power Supply: Servo Battery Nickel Metal Hydride: Ni-MH Supply Voltage: 6.0V Supply Current: 2800mAh Dimensions:1.875 x4.375 x Weight:.58 lbs Price: $22.95 This battery pack is perfect for small robots, it almost offer twice the run time that a AA pack provide, it is light and fairly small. Just of the charger, the supply voltage is

42 Power Supply: Electronics Batteries Nickel Metal Hydride: Ni-MH Supply voltage: 12V Supply current:1600 mah Dimension: 2 x3 x Weight:.70 lbs Price: $

43 Power Supply: Voltage Regulators LM317T Input voltage: V Output voltage: V Output Current: 1.5A Price: $.48 each /DigiKey It is a fairly common and useful voltage regulator Adjustable Voltage Regulator

44 Power Supply: Voltage Regulator cont. This is the schematic for the LM317T The output voltage is controlled by R1 and R2 The capacitors are used to provide a steady and stable input and output voltage The equation for the output voltage is VO = 1.25V (1+ R 2/ R1)+IadjR2 LM317T

45 Power Supply: Schematic

46 Budget Components Price Quantity Subtotal Servomotor (6) Chassis Leg (2) Microcontroller Basic Atom Pro Xbee Modules Xbee Module Adaper Battery LM317T Color Sensor Servo Controller PS2 Controller Free Pic Axe 18X Total

47 Questions?