Robot Design Workshop: VEX Hardware & Robot Building Basics

Transcription

1 Robot Design Workshop: VEX Hardware & Robot Building Basics Nik Kukert Bison BEST Robotics 1

2 Basics Only use parts supplied in the consumable and returnable kits (or approved optional items) Robots containing additional parts will be disqualified Do not modify returnable parts No paint, tape, etc. may be placed on these parts (except residue-free painter s tape) Robot must fit into a two-foot cube (initially) and weigh less than 24 pounds Robot components may extend outside two-foot cube after game starts All machines will be inspected for compliance prior to competing 2

3 Returnable Kit Items Servos Analog WiFi key USB/Tether Serial (4) Servo Extensions Joystick AAA Battery Charger Digital i/o Motors/ Servos (2) (2) Controller Battery USB A-A cable (2) (2) Servo Horns Servo Power Adaptor Cables (16) 3

4 Returnable Kit Items Drive Components (2) Motors 7.2V Battery Charger (2) Motor Controller (4) Battery Adapter Screw Terminal Sensor i/f Cable (8) (2) 7.2V Battery Screw Terminal Motor i/f Cable (4) (2) 4

5 Example Hookup DC Motors Motor Screw Terminal Cortex Controller Battery Motor Controller Servo Include a Servo Power Adaptor Cable (not shown) 5

6 VEXnet Control System VEX Cortex Microcontroller Dual ARM Cortex CPUs Programmable WiFi Radio Technology 6

7 VEXnet Cortex M3 Controller 8 Analog inputs WiFi Proprietrary Comm 12 Digital Inputs or Outputs Standard Serial Interfaces (UART, I2C) Speaker Output 10 Motor/Servo Ports (Only use Ports 2 9) System Status Indicators Retaining Clips can be removed to install cables 7

8 VEXnet Joystick Playstation Game-Style Controller 8 Buttons on Top 2 XY Analog Joysticks Power Switch 6 AAA Rechargeable Batteries Plug-in USB/ WiFi Key 4 Buttons on Front-Side Programming Interface 3 Axis Accelerometer (XY Tilt, XYZ Accel, Shake) 8

9 VEX Cortex Connectors Gnd (Blk) +5v (Red) Sig (Wht) USB Standard Serial Interfaces (UART, I2C) Analog In Digital In/Out Speaker Out SP wire motor (Do not use) 3-wire PWM Servo/Motor Ctrl wire motor (Do not use) Sig (Wht) +5v (Red) Gnd (Blk) 9

10 DC Motors Four motors are supplied in the kit Two large motors and two small motors Motors can be used to power wheels, lifting arms or mechanisms, grippers, etc. Motor mounting brackets and screws are supplied in the Consumable Kit Tabs can be easily bent to mount motors on different surfaces 10

11 Motor Mounting Brackets Use of motor mounting brackets to mount the motors is no longer required. However, they are HIGHLY recommended! if they are not used when face mounting the motors, it is easy to damage the internal gear plate. 11

12 DC Motors Four External Motor Controllers supplied in the Returnable Kit (these MUST be used) Connect via 3-wire external motor controller and 2-wire screw terminal cable (red/black) Use motor ports 2 thru 9 only! Do NOT Use the Built-In Motor Controllers Motor ports 1 and 10 Motor amperage may damage circuitry 12

13 DC Motors Servo/Motor Ports are Divided into 2 Banks Bank 1 = Ports 1-5 Bank 2 = Ports 6 10 Use only ports 2 9 Each bank can support a maximum of 4 amps of current BEST large motor stall current can reach 3.5 amps For Power Reasons, Spread Motors among Ports No more than 2 motors plugged into ports 2 5 No more than 2 motors plugged into ports 6 9 Otherwise you risk overcurrent and shutdown of the processor Sheet Metal Shield around the Large Motors IS Needed and Should NOT be Removed 13

14 DC Motors Connect wires to motor terminals Quick-disconnect terminals (Strongly Preferred!) Solder Polarity is NOT marked on motors: positive (+), negative (-) Wiring (and programming) will determine clockwise or counter - clockwise rotation for positive stick movement Recommended to mount motors using supplied brackets and 8-32 machine screws Machine screws must be cut to proper length to avoid motor damage (use screws supplied in kit)! Max screw depth= ~1/8 (small motor) ~1/4 (large motor) 14

15 3-Wire Motor Connection Suggest using painter s tape or heat shrink tubing here External Motor Controller Standard 2-wire Motor Cable Standard 3-wire PWM connector Screw Terminals for attaching motor leads 15

16 3-Wire Motor Connection Connectors are not keyed Connect red to red, black to black 16

17 Servos Servos produce a specified rotational movement when activated Possible Uses Activation of microswitches Operation of grabber mechanisms Release of a springloaded latch 17

18 Servos Futaba S3003 or S3004 Series Maximum 120 degree rotation (+60, -60) Connection to Cortex Controller Via 3-wire Servo Power Adapter cable Prevents damage to servos Use motor ports 2 thru 9 only Servo Horns may be modified Servo Horns Do not overtighten mounting screws! (2) (2) (1) 18

19 Motor/Servo Connectors Placement of Servo Connectors VEX motor controller can be placed adjacent to a Futaba servo or extension connector 1) Keyed differently; will work but a tighter fit. 2) Recommend keeping motor controller in a higher numbered port; may lose one servo port due to this. Futaba servo & extension connectors ARE keyed BUT they will still fit in backwards. Pay attention to the keying and wire orientation (white wire to the inside)

20 Electrical Connections No-residue painter s tape may be used to secure VEXnet key and cable-to-cable connectors (or other parts as needed). Painter s tape included in the Consumable Kit 20

21 LED Status Lights Joystick Battery Status Robot Battery Status Communication Link Status Game Status (not used by BEST) Green Battery good charge Yellow Battery - dying Red Battery dead Green VEXnet communication established Yellow VEXnet searching Lights on the controller and the joystick are the same 21

22 Re-Syncing (Pairing) VEXnet If VEXnet does not connect, you may need to re-sync the joystick/controller pair by simply connecting a USB cable and powering on both units. 22

23 BEST Programming Options Three different programming environments available easycv4 RobotC Mathworks MATLAB/SIMULINK easyc is a block programming environment (similar to software for Lego Mindstorms) RobotC programs in C with a text editor, but it has runtime debugging (can step through program line by line and see what the results are) SIMULINK is graphical programming/modeling environment with simulation capability (see what your program will do before you download it to the Cortex) 23

24 Out of the Box Configuration Cortex Controller comes pre-installed with a default program. Allows a team to hook up the Cortex and have it work without having to program it. Referred to as the BEST default program. This is NOT the only configuration for the Cortex! Good for initial checkout, but we want teams to load a unique configuration. 24

25 Downloading a Program Direct USB Download Uses only the A-A USB cable. Battery is not needed 25

26 2015 Kit Updates Video Capture Devices (e.g. GoPro) are allowed on the robot (see Generic Game Rules ) New Belt & Pulley Kits (now called Motion Components) offer improved strength and durability Added ¾ Foam Board to Consumable Kits 26

27 Kit Issues Secure cables/wiring to prevent stress at the connections 27

28 PowerPole Connectors connect/disconnect here leave connected here 28

29 Team Tips Use quick-disconnect terminals to attach wires to motor terminals (preferred). If using solder, tin motor wires before attaching to screw terminals since frayed stranded wires can cause a short. Do NOT solder wires to Cortex connectors! Sensor cables, servo wires, and servo extensions are all keyed in correct orientation; insert and remove carefully to avoid destroying connectors (pin connectors are very delicate). Tighten screws on motor and sensor connector cables so that wires are not loose and do not pull out. Mount Cortex to robot using #8 screws through holes provided; be careful not to over tighten. Avoid hot insertion of USB Keys. You may operate tethered by removing the USB WiFi key and connecting a USB A-A cable between joystick and Cortex. 29

30 Joystick Calibration If the motors hum or creep (sticks not returning to zero), the joystick may need to be recalibrated Calibration procedure (as extracted from the easyc help file): 1) The Joystick must be "Linked" to the Cortex Microcontroller using the VEXnet Keys. 2) Hold the "6U" Back Switch depressed. 3) While the "6U" Back Switch is depressed, use a small Allen Wrench (1/16" or smaller) or similar small straight tool to depress and hold the CONFIG Switch. 4) Hold both Switches depressed until you see the Joystick LED Flash RED and GREEN - you can now release both Switches. a. There is a 10 second time limit to complete the following steps 5 and 6. 5) Now move both Joystick Pots to the maximum position desired in all 4 directions - Up, Back, Left, and Right. a. If a movement is not detected in all 4 directions, a timeout will occur after about 10 seconds and the Cal Mode will be discontinued and the VEXnet LED will briefly Flash Red. b. The Joystick LED will continue to Flash RED and GREEN during the calibration process. 6) After movement is detected in all 4 directions, the Joystick LED will be ON and Solid GREEN. a. To "Save" the Calibration, depress and release the "8U" Top Switch Button. b. If the calibration is accepted and Saved, the Joystick LED will start Flashing Fast GREEN for a few seconds. c. If the Calibration is not Saved, a timeout will occur after about 10 seconds and the Cal Mode will be discontinued and the VEXnet LED will briefly Flash Red. d. To cancel a calibration, depress and release the "7U" Top Switch Button. The Cal Mode will be discontinued and the VEXnet LED will briefly Flash Red. e. If the Cal Mode is discontinued or saved, the Joystick LEDs will resume their normal function after the VEXnet LED briefly Flashes. 30

31 Design Basics: Chassis Chassis (plywood or PVC) Wheels Motors Use plywood or PVC to create a chassis. Other components will be mounted to the chassis. PVC is a thermoplastic. It can be heated and reshaped into any configuration. Two large motors can be used to power drive wheels. Robot will move forward, backward, or turn by varying relative speed and direction of each motor. Allow non-drive wheels to pivot to make robot maneuverable. 31

32 Wheel Attachments Some proven techniques for mounting drive wheels to motor spindle. Other techniques can be used. 32

33 Wheel Size Experiment with size of wheels. Large wheels: Faster robot More difficult to control Small wheels: Slower robot Easier to control Various materials are included in the consumable kit which can be used to enhance traction. 33

34 Lifting Mechanisms Many mechanism designs can be created to lift or retrieve objects. Belt and Pulley Slide and Rail System Scissors Lift Parallel Arm Linkage 34

35 Linear Drive Mechanism Rotational motion of motor can be used to create a linear drive using belts and pulleys. 35

36 Grabbing Mechanisms Simple grabbing mechanism can be operated by a servo, allowing motors to be used for lifting mechanisms. Servo with Servo Horn Pivot As Servo rotates, grabber arms open and close Wires attach arms to Servo Horn 36

37 Reminders Read Generic Kit Notes Read Generic Game Rules Read Game-Specific Rules Re-read all of the above! 37

38 Where to find help? Online documentation (BRI Site) BEST Public Message Board (for anyone) Must register for login account Share ideas, resolve issues, Official Q&A Control System Category Use Official Q&A page during contest for rules specific questions Is this legal? VEX Forum Technical questions about VEX equipment easyc and RobotC dedicated forums included here 38