Hi Guys, I (RobosapienV2 4mem8) thought I would put up some photo's of a weekend project making a robotic base. This project would be a good exercise for members and others in constructing a simple robotic base. The base is constructed of alloy, the wheels from an R/C toy and casters which were lying around, some parts have to be made. Motors and motor drivers will vary depending on what you have or install. This is for the basic frame only. I have included the finished robotic base photo. The rest of the details on how to build it will follow underneath.Bare with me as these images are going to take a while to upload over a period of time.
1 Frame assembly
2 Wheel assembly
3 Installing the motors
4 Fitting the casters
5 Installing the motor controllers
6 Installing some of the electronics
7 Making the Perspex base
8 Installing the batteries
9 Installing the electronic brains
10 Installing the IR detectors
11 Installing micro switch bump sensors
12 Installing the distance sensors
13 Fabricating frame
14 Installing Flexi glow rods
15 Watch the video
16 Mounting RSV2 on base
17 Modified RSV2 sensors
18 Shoulder laser cannon and WIFI camera sight
19 P/S 12v to 9v + 6v,3v, + 6v, for laser's, and 4.5 + 5v spare
20 Connecting power supply to RSV2 and robotic base
21 installing RSV2's spare foot and tilt sensors
First cut 2 pieces of 50mm x 25mm alloy U section 296 mm long and two pieces of 30 mm x 25 mm angle alloy 300 mm long. Next mark the centre of the of 50mm x 25mm u section both sides. The height from the bottom of the alloy will depend on the wheel diameter. Bore a 10 mm hole through both sides on both pieces of alloy, These will be the holes for the bearings. (This hole will depend on the bearing used) In this case they are f/b oilite bearings (you can use stepped ball bearings, These are the one's that have a stepped outer flange which you will need to rest against the alloy) these bearings will accept a 6mm shaft.
Next you will need to lighten the alloy sides, I masked with masking tape both sides and plotted out evenly spaced holes and allowing for a 12mm drill bit. Once marked you will need to hold the alloy in a machine vice and proceed to drill all the holes right through both sides. When that is done clean the holes edges with a modelling knife. Next mark the front and back angle, Place the 30mm x 25mm angle alloy [30mm facing up] at the front and back of the 50mm x 25mm alloy and mark the bottom edge, this is the starting mark and draw a line so that it will miss the 12mm holes, then cut with a hacksaw and clean up the edge with a file. Take no notice of the white cog on the end on the shaft as this was there to stop the shaft from falling of.
Next we have to bolt all the pieces together, take the angle alloy and place on top of the 50mm x 25mm alloy with the 30mm angle facing downwards clamp together and drill two holes in each corner using 5mm x 15mm bolts and secured with 5mm nylock nuts, now we have our basic frame.
These are the parts for the wheel assembly, Top 8mm load axles, f/b oilite bushes, 5mm s/s wheel axles, 8mm lock blocks to clamp 8mm shaft to the 4mm motor shaft, washer spacers. The 5mm s/s wheel shafts are tapped and threaded into the 8mm load axles. The load axles were made from 8mm s/s steel and are 60mm long, one end has a hole bored to 4mm and the other end is bored to 4.5mm and threaded.
The lock blocks and f/b bushes are from old printers that held the cartridge shaft to the DC motor. I used to wreck old printers and pc's for their parts, These were the days when pc's were the size of your average pc desk, lots of parts nuts and bolts etc.
Wheel with 5 mm s/s bolt tapped into the 8 mm shaft, note the slot in shaft for the clamp to tighten on to the 4 mm motor shaft.
Wheels used from an old R/C Jeep. Remove old axle and thread the hole with a 5 mm tap.
A closer look at the clamps to clamp 8 mm axle to 4 mm motor shaft.
Next insert the oilite f/b bearings these should be a press fit, they have a small notch to one side, once the holes are drilled file a small notch this will locate the bearing and stop it from rotating. Note the f/b bearings are from old printer cartridge units I collected these in the 80's. So unless you can source these I would suggest using flanged bearings.
Side view of finished wheel assembly. Good advertising!
Wheel assembly finished waiting for the motor to be mounted. (ignore the white cog, just there to hold axle in place).
INSTALLING THE MOTORS
Depending on what type of motors you use the holes or brackets will differ from what is shown here, The thing to watch is that you align the motors correctly with the shafts so as not to have any binding. In this case I have drilled 4 3 mm holes that correspond to the bolts on the motors.
The motors used here are Como drill pile drive type with stackable gearboxes and voltage levels of 3,6,9,12, and 15v with these variable voltages and stackable gearbox's we have a great deal of different rpm's and torques.
Here I have disassembled one of the gearbox's to fit it to the holding bolts as with the other one in place I could not install in one piece.
Both motors now installed.
Notice the two clamping plates holding the 8mm shaft to the 4mm motor shaft.
FITTING THE CASTERS.
These casters were lying around the basement so used these. First cut 2 pieces of 20mm x 25mm x 20mm DOUBLE angle alloy drill a hole in both pieces to accommodate the shaft of the caster, use two nuts and washers, use these as spacers to adjust the height of the caster when setting up. Now drill two more 5mm holes to attach the 20mm x 25mm x 20mm angle to the base plate. Once both are fitted turn base plate over on a flat surface and adjust the nuts and washers so that the base plate is firm on all four planes.
Both casters now installed and adjusted.
A closer look at the caster assembly.
Flat and level, Make sure that when slight pressure is applied to the casters both ends that there is friction on the main wheels and that they do not spin. They should grip the floor.
INSTALLING THE MOTOR CONTROLLERS.
These are HB 25 controllers from Parallax, They can sink 25 amps and can be used to control DC motors they use 3 wires from the basic stamp to control the controller,+ 5v gnd and signal. There is a separate voltage to the controller 12v to power the motors.
Cut four pieces of 30mm x 25mm x 20mm wide alloy as holding brackets, I used four instead of two longer brackets as this gave me flexibility for installation. Once mounted on the controllers they are then mounted on the side of the base frame or in a convenient place.
Both controllers fitted.
A closer view of the controllers.
Notice the cooling fans under the controller.
INSTALLING SOME OF THE ELECTRONICS.
This is the subsumption board from Bluebell Design, Basically this off loads some of the hard work from the main BS2P-40 stamp to control the motors, IRPD sensors and bump sensors, It's a pre programmed pic chip which can operate 8 servo outputs and four A/D inputs.
Installing some cross bracing flat alloy 15 mm to support the electronic boards.
This is the final stage that I have reached so far. Shown here is the Parallax professional dev board with the BS2P-40 chip this is connected to the subsumtion board. The BS2P-40 has 32 I/O so far I have used only 4 leaving 28 I/O left. I intend to fit ping ultrasonic, PIR sensor, two digital voice recorders, camera, LCD display, pan/tilt for camera. This is where things slow down for me as I am NOT a programmer although I am learning pbasic. I have the code for the subsumption and bs2p to run this machine with motors, IRPD sensors and bump. What I need now is your help in integrating the pan/tilt , ping and PIR code into the subsumption code as I am not sure where to install this to make the motors correspond to what the ping, PIR and camera sees.
The base unit is going to have a Plexiglas circle covering the top of the base unit and the bump sensors in a quadrant style, Batteries will be placed underneath, two 6v gellcel and a 3000nmh pack for the electronics. These will be installed next. This weekend I hope to install the batteries and the Plexiglas disc. This will give more area to accommodate the electronics.
This whole project + motor controllers (Believe it or not) was constructed in a weekend except for the installation of the electronics.
Cost so far (EXCLUDING any electronics and motors), includes Plexiglas top for base. $75.00 NZ Most of this was in the Plexiglas
$38.00 as this consists of two discs 300mm diameter the second disc is cut into 4 semi circles and is attached around the alloy base under the top piece of Plexiglas.
MAKING THE PERSPEX BASE.
From the last installment I have removed the electronics to make the Perspex base.
Tools you will need for this are: A wood router with a 12mm straight cutter and ball race at the end. access to a band saw or jigsaw and a drill press or cordless drill.
You will need 20 threaded brass standoff's with a thread length of 10 mm.
These are inserted around the alloy base with nuts and spring washers.
Standoff's have been placed all around the alloy base 12 in total, These are used for securing the Perspex base to the alloy frame and also can be used for fixing circuit boards or alloy framing for the next tier.
Next you will need two pieces of MDF (Medium Density Fiberboard) 400 mm sq. Next draw a line from the diagonal to find the centre of both pieces of MDF. Using a compass draw a 300 mm circle on both pieces of mdf, Band saw just proud of the line and using a disc sander or by hand sand the edge's till smooth. This is now your template for the router. Cut two pieces of Perspex 400 mm sq, drill a hole in the centre of both the mdf and the Perspex, larger hole in the Perspex for a screw as we want to place the mdf on top of the Perspex and screw them together. When cutting out the Perspex make sure that you cut it larger than the MDF by 2 mm.
Next using the pattern as a guide router out the Perspex and you should end up with a neat disc like this.
Next place the Perspex on top of the alloy base and centre it so that the alloy edges just touch the outside of the Perspex, Now locate the 12 brass standoff's under the Perspex and mark where to drill the holes to screw the Perspex down.
Next using the other piece of MDF mark out the 300 mm sq alloy so that the four points touch the radiused edge, Draw a line around the base and mark out where the wheels are and allow clearance around the wheels. Next cut the MDF as shown in the picture so you have four patterns. Cut the Perspex 2 mm larger than the patterns, Using small G clamps line up and cramp them together, Using the router again router out all four pieces of Perspex.
You should now have four pieces of Perspex like this.
Using masking tape cover the edges and mark out 12 evenly spaced sections..
Using the other four Perspex pieces cramp them underneath the top Perspex and drill 3 mm holes right through
You will need 32 10 mm threaded standoff's and 32 small bolts with the same thread.
The bolts on the right need to have the heads cut off leaving a thread length of 12 mm, Insert two standoff's on each side of the thread leaving 4 mm of thread showing in the centre.
Now insert all the standoff's in the top Perspex so they hang down, Turn over the bot and locate the four other Perspex plates and bolt up.
You should end up with it looking like this. In between the Perspex this is where the bump sensors will be housed.
INSTALLING THE BATTERIES.
These are the alloy holding straps for the batteries 20 mm x 1.5 mm these will vary in length depending on what batteries you use, Notice the score marks indicating the battery width and height, These are also for bending purposes.
This is how they should look when finished.
Installation of alloy battery holders from underneath and top views.
Two gel cell batteries are used here: 1 X 12v 3.4ah for the motors and a 12v 1.3ah for the electronics, It is always a good idea to keep the two power sources separate to avoid interference from the motors.
Batteries now in place.
Note: The batteries have had there spade terminals bent straight up, Four holes are bored in the Perspex so that the terminals come through the top of the Perspex.
A central hole has also been bored to allow the motor and motor controller wires to come through.
A 12 way terminal block has been fitted here to take the motor wires, also not shown will be the fuse area.
Note: This project is now into it's second weekend.