Robot Platform Design Instruction

Mechanical Construction

This robot is made of an easy-to-build frame, using various lengths of L and I shaped aluminum extrusions. The numbers and dimensions for each extrusion are shown on the drawing available here

These extrusions are available in most hardware stores and require little more than cutting, filing and drilling. The two bottom extrusions that hold the motors require special attention and extra cutting to allow precise mounting of the motors. Assembly is done for the most part using pop rivets.

Hardware needed:

• L and I shaped aluminum extrusions, per drawing
• ¼ x 0.5” screws
• ¼ retaining washers
• 1/8 diameter x ½ long, and 1/8 diameter x ¾ long pop rivets
• 4 x DC motors-NPC 2212 with 4 x 6" wheels

Follow these steps to assemble the robot’s chassis:

1- Cut all the L and I shapes listed on the main drawing to the prescribed length. See:

Robot drawing

2- Prepare the two bottom L shapes by first cutting a notch on the side to allow for the motor axle to go through. Mark and drill the 4 holes needed for mounting each motor. See:

Drawing of of bottom L-shape extrusion with motor cut-out
Photo of bottom L-shape extrusion with motor cut-out
Motor CAD drawing
　

3- Arrange the front and rear L shapes so that they are at a right angle with the shapes holding the motors. Drill the two holes for each motor.

4- Position the motors on the frame. Cut the axle on the unused side.

5- Screw the motors in place. Verify that the extrusions are at a right angle and tighten the screws. See:

Photo of bottom frame with 4 motors

6- Place two rivets at each corner as shown in the drawing.

7- Position the two battery holding rails as show on the drawing. Use the actual batteries to ensure that you have the right width. Drill and fasten with rivets. Position and fasten the two small L shapes at each end of the batteries to prevent them from sliding from side to side.

8- Position, drill and use rivets to fasten the bottom transversal, and risers on the corner

Photo of bottom with transversals
Photo of top with raisers

9- Built the top frame by positioning the four L extrusions at a right angle and fastening with rivets. The top frame, which will not be screwed or riveted, will be placed on top of the raiser for easy removal.

10- Cut a piece of clear Plexiglas the size of the outer upper frame. Fasten in place using 10 rivets.

Photo of complete frame with cover

11- Build the Motherboard stand by assembling the L and I shapes shown on the drawing. Fasten the stand on the frame using rivets.

Tools needed:

• Metal saw and file
• Electric drill with ¼” and 1/8 drill bits
• Rivet gun
• Right angle

　

Mounting the Electrical Components

Components Needed

• Roboteq AX2550 DC Motor Controller
• VIA EPIA ME6000 Mainboard
• iTuner PW60 power supply with extension wires
• 2.5” notebook drive with 5G or higher capacity
• 802.11b or better PCI wireless LAN card
• 1 dual throw, bipolar 20A switch for use as master switch
• 1 three position mini-switch for controller power control
• 1 momentary, normally open, pushbutton switch as mainboard power switch
• Optional low-power relay and protection diode
• LEDs with resistor

Mounting Instructions

1- Motors should be mounted at the time of the frame assembly.

2- Position the controller as shown on the drawing. Mark the position on the holes and drill the four mounting holes. Bolt the controller using ¼ screws and nuts with a nylon end to prevent the screws from becoming loose due to vibrations

Photo of robot with controller

3- Place the batteries inside the rail. If needed, add a strap to hold them in place, especially if the robot is expected to move over rough terrain.

4- Drill 4 holes for holding the 2.5” disk drive on the bottom frame. Insert drive and screw in place.

5- Position Power Supply as show on drawing. Mark position of the holes. Drill two holes and tap two threads. Insert riser. Place power supply and screw in place.

6- Place the mainboard at the desired position on the stand. Mark the position of the holes. Drill 4 hole and tap 4 threads. Insert risers. Place motherboard on top of them and screw in place.

Photo of robot with wired motherboard

7- The drawings do not show mounting hardware for the camera as each camera, differs from another.

8- Remove the mounting bracket from the PCI wireless LAN card and insert in Mainboard slot.

9- Drill holes and mount Master Switch, Motor Controller Switch, Mainboard power switch, and on the side of the bottom-right L shaped extrusion.

　

Wiring the Robot

Hardware needed:

• Red and black AWG10 wires
• Miscellaneous wires
• Connecting electrical nuts

Examine and follow the electrical wiring diagram available here. Connect the wires and components as indicated. Below are a few useful explanations and instructions.

1- The robot uses two 12V batteries. One is dedicated to the motors, the other to power the motherboard. The dual battery configuration will let the motherboard run as long as its battery is above 10V, regardless of the motor battery's charge. Depending on driving conditions, the motor battery can be drained very quickly. Furthermore during quick acceleration, collisions or high load conditions, the motors will make peak demands on the battery which could cause temporary drops in battery voltages that should be isolated from the mainboard power supply.

2- A main switch is used to cut power from each battery to the controller on one side and to the mainboard power supply on the other.The other side of the switch goes to two diodes that are joined to a wire on which a battery charger may be connected. The two diodes allow the current to flow from the charger to both batteries while preventing one battery to flow into the other during normal operation. The switch will connect the batteries to the charger only when the motherboard and controller are off. This is to prevent the charger's voltage, which can raise significantly above 12V, from damaging the mainboard's power supply. If, instead of a battery charger, you use an electronic power supply which will never exceed 12.5V, the diodes may be connected directly to the batteries, so that the robot can be operated while power is brought from the outside.

3- A three way switch should be used to control the power of the controller. Using such a switch, the controller can be independently turned off or on, or may be turned on upon the motherboard being turned on.

4- A low power 5V relay should be used as shown so that the controller turns on or off as the mainboard is turned on and off (and not just when the master switch is on). The relay's coil must be connected to a 5V pin available on the mainboard's header. This relay is optional. If omitted, the red wire going to the Controller Switch should be connected to the mainboard's battery. This will ensure that the controller's electronics have adequate voltage even if the motor batteries are discharged.

5- The controller has a built-in voltage sensor to monitor its battery. To monitor the mainboard's battery, two resistors are used to create a voltage divider which is then connected to the controller's analog input 1. This important capability will let the operator know how much charge is left in each battery.

6- You will need to build a custom RS232 wire for connecting the controller to the mainboard, as well as for connecting the analog port to the battery voltage monitoring point. Note that there are two general purpose digital inputs, one additional analog input, one low power digital output and one 2A digital output on the connector that can be used to connect additional sensors and actuators to the robot.

7- The mainboard power supply is a special board that will convert the battery's 12V into the 5V, 3.3V and other voltages found on ATX power supplies. For higher reliability, the power supply model selected selected in this project is bolted on the robot chassis and an ATX power supply extension is used to connect it to the mainboard.

8- A 2.5" notebook must be used inside the robot because of its light weight, smaller size and lower power consumption. Notebook drives are also beneficial because they use 5V only, vs. 5V and 12V for 3.5" drives. The power supply cannot deliver a higher voltage than the battery, meaning that the 12V output will very quickly drop below safe levels for reliable operation of 3.5" drives. The 5V output will remain stable, and therefore the disk will operate reliably, as the battery voltage drops to as low as 10V or less.

9- To power the mainboard, you will need to turn the master switch to On, and then press the ATX power pushbutton switch. Turning the mainboard off should be done using an orderly shutdown from within Windows or the application software.

10- A couple of LEDs should be added to visualize whether or not the Master power is on, and if and when the mainboard is on. Connect two LEDs with two 470ohm resistors as shown on the diagram. The LED monitoring the mainboard should be connected to one of the headers with a 5V and ground pin.

11- Connecting the camera is as simple as plugging the cable into the USB port. The notebook drive should be connected as a master on the IDE1 port. Remove the faceplate from the wireless LAN card and plug it in the PCI slot.

12- Wire the motors as shown.

Photo of fully wired robot
　

Installing and Setting up the Software

Software needed:

• Operating systems (Windows 2000 recommended). OS includes Microsoft Netmeeting used for video transmission
• Drivers for Camera and Wireless LAN Card
• VNC remote desktop software
• Roboteq's Roborun 1.4 (beta) software

For expediency and availability reasons, the robot platform is based on the Microsoft Windows operating system. Eventually a different operating system, such as Linux, would be preferred, but Windows will let you get a working robot in a few hours using commercial software. While any recent version of Windows would be adequate, the information below is based on using Windows 2000.

1- Temporarily connect a mouse, keyboard and monitor to the mainboard. This will be necessary for the first part of the installation.

2- Install Windows 2000. Connect a CDROM drive to the motherboard. For more convenience, it is recommended that you do this installation of the motherboard on a bench rather than inside the robot. Install the drivers for the webcam and the wireless LAN card. You may remove the CDROM drive after this installation.

3- Set up the Wireless LAN card. If the robot is to talk directly to the laptop, then configure both the robot and laptop cards for Ad/Hoc communication. Assign a name to both cards, choose a channel (e.g. 6). Assign a fixed IP address to the wireless LAN card of both systems by going to the Start>Setting>Network and Dialup Connections select the Network Adapter, TCP/IP and Properties. The IP addresses must be in the same subnet, for example 10.10.10.10 for the robot, 10.10.10.20 for the laptop.

4- It is recommended that you establish a wired LAN connection, although this is not mandatory. The EPIA mainboard has an on-board 10/100 Ethernet port which you may use as well. Preferably, give the LAN card a fixed IP address. Use an IP address that is in your existing subnet if you have one. You may use an arbitrary one otherwise (e.g. 20.20.20.20).

5- Verify that the network connection works by typing "ipconfig" is a command mode window. This will list the network cards found in your robot or laptop and the IP addresses assigned to them. Send ping commands from one system to the other and make sure that there is a reply.

6- Launch Netmeeting on both the laptop and the robot. Netmeeting is installed on all Windows systems and can be found in the Start>Programs>Accessories>Communications menu. On the laptop, configure Netmeeting so that it runs in the background (waiting for a call) when closed. Configure the video setting so that the video is automatically sent when Netmeeting runs. Configure Netmeeting to automatically accept calls (note that when Netmeeting restarts at system boot, the "automatically accept call" option will be disabled again).

7- Install the Roborun software on the robot. Make sure the controller is powered on and run the main program from the Start>Programs>Roboteq menu. The program will try to establish communication with the controller and report its software revision number. Change the settings to "RS232" in the input command mode and set the motor control mode to "Mixed". Save the settings in the controller and exit Roborun.

8- Install the Roborun Software on your laptop. It will be needed to operate the robot.

9- Drag a copy of the "roboserver" program from Start>Programs>Roboteq to Start>Program>Startup. Roboserver is a small program that "listens" to the network and relays commands and data from Roborun running on the laptop to the controller connected to the robot's mainboard. Roboserver will start automatically when the robot boots.

10- Install VNC remote desktop software on both the robot and the notebook. Drag a copy of the VNC host software Run "WinVNC (App Mode)" from Start>Programs>VNC to Start>Programs>Startup. Run the program once and create a password. Run the VNC Viewer on your Notebook, and at the prompt enter the IP address of the robot followed by ":0" (eg. 10.10.10.10:0); then enter the password. You will then see a copy of the robot's desktop screen on the notebook. Ky strokes and mouse movement on the Notebook will actually take effect on the robot. From now on, you will be able to do any administrative work on the robot's mainboard from the notebook. You will no longer need to have a keyboard and monitor connected to the robots.

　

Operating the Robot

Follow the instructions below to operate the robot.

Powering On
- Turn master switch on. The Master Power LED will light.
- Turn the motor controller switch on if you are ready to drive.
- Press the ATX power switch. The LED on mainboard will light. The board is booting.
- Wait a couple of minutes for the boot to complete and the applications to start. Unless a monitor is attached, you will not see the boot sequence.

Dialoging with the robot using VNC via LAN or WLAN
- VNC will be running on the robot automatically when boot completes.
- Launch VNC viewer on laptop.
- Connect to laptop using its IP address followed by ":0".
- Enter the password.
- Laptop now is in control of the robot's screen and keyboard.

Creating Video Link
- Use keyboard or VNC to launch netmeeting on robot. Netmeeting must be set in "auto answer" (see selection in File menu). Netmeeting will remain in auto answer mode until the mainboard is shut off.
- Quit VNC.
- Launch netmeeting on laptop. Place the robot's IP address in the address window and press the call button
- Connection will be established. The video should automatically come from robot.

Remote controlling the motors
- Launch the Roborun software on the laptop.
- Change COM/LAN port. Select LAN and enter robot's IP address. The upper right of the Roborun screen will indicate if connected or disconnected.
- Click on the "Power" tab. Check the "External Voltage Monitoring" box.
- Click on "Run" tab. Click on Run button.
- If you move the cursors, the motors should move.
- If a joystick is installed, enable it by checking the joystick box. Now the motors should follow the joystick movement. The chart and display windows will show Amps consumption, voltage, temperature and other operating parameters.

Shutting down
- Create a VNC connection and shutdown using Window's shutdown button
- When the mainboard is off, shut off the Master Switch

Charging the batteries
- Connect the battery charger. Batteries will charge only when the Master Switch is off.

Improving your Robot

The VIA-Roboteq robot platform described here must be considered as a basis upon which to add functionality and intelligence. The 600MHz EPIA miniboard has sufficient computing horsepower to perform extremely sophisticated pattern recognition, navigation and other functions needed for truly autonomous operation. The list below is a sample of natural enhancement to this robot:

- Eliminate the hard disk by booting the OS from an USB pen drive or Flash card.
- Use and open source Operating System such as Linux.
- Add navigation instruments such as GPS, compass, and sonar.
- Do image recognition.
- Add speech and sound via the Mainboard's sound card.
- Carry and operate a robotic arm.
- and more.

相关链接：http://www.roboteq.com