Biped BRAT Assembly Guide.

Updated 04/02/2008.

Safety first! Wear eye protection and never touch a powered robot!

Note, you will need to make a mirror image of the steps shown to complete the biped. The steps illustrated show the robot's left leg.
Image of Biped BRAT.
 
Step 1.
Attach a multi-purpose bracket to the foot as shown, using three 2-56 x .125" screws and 2-56 nuts.
 
3 x 3 x

Figure 1.
 
Step 2.
Attach the "L" bracket to a short "C" bracket as shown, using two 2-56 x .250" screws and 2-56 nuts.
 
2 x 2 x

Figure 2.

Step 3.
Attach a multi-purpose bracket to the "L" bracket as shown, using two 2-56 x .250" screws and 2-56 nuts.
 
2 x 2 x

Figure 3.
 
Step 4.
Your two leg assemblies should look like the image so far.
Figure 4.
 
Step 5.
Attach the assembly from Step 3 to the multi-purpose bracket on the foot. See figure 5-1 for detailed information.


Figure 5-1.
Figure 5-2.

Step 6.
Your two assemblies should look like the image so far.


Figure 6.
 
Step 7.
Connect two short "C" brackets as shown, using two 2-56 x .250" screws and 2-56 nuts.
 
2 x 2 x


Figure 7.
 
Step 8.
Attach the "C" brackets to the leg assemblies as shown. See figure 8-1 for detailed information.


Figure 8-1.


Figure 8-2.

Step 9.
Attach a multi-purpose bracket to the "C" bracket as shown. See figure 9-1 for detailed information.


Figure 9-1.
Figure 9-2.
 
Step 10.
Attach the leg assembly from step 9 to the 3" U-Channel as shown, using three 2-56 x .250" screws and 2-56 nuts.
 
3 x 3 x

Figure 10.
 
Step 11.
Your assembly should look like the image so far. Note, in the image the robot is face down.
Figure 11.

Step 12.
To maintain compatibility with our program, the robot legs have to be mechanically aligned. To do this move the servo to its center of rotation using the Bot Board, SSC, or other servo controller or microcontroller. We have set up a tutorial to guide you through this step. If you are using a different microcontroller, consult your electronics documentation for help with this step.

Note, centering a servo simply requires generating a 1.5mS positive going pulse that repeats every 20mS.
Figure 12.
 
Step 13.
Install the two ankle servos as shown, using the included 3mm hardware, two #2 tapping screws, and the diagram below. For quick prototype assembly, you can use rivet fasteners (sold separately: NSRF-01) as illustrated. Make sure that the servos are centered before attaching to the "C" brackets. Note, your servos may be a little off. We will fix this with the calibration procedure in the Sequencer software.
 
4 x  


Figure 13.
 
Step 14.
Install the knee servos as shown. Use the #2 tapping screws and the diagram below. Make sure that the servos are centered before attaching to the "C" brackets.
 
4 x  


Figure 14.

Step 15.
Attach the 3/4" standoffs to the electronics carrier using four 4-40 x 1/4" hex socket head cap screws.
 
4 x 4 x


Figure 15.
 
Step 16.
Attach the 5/16" standoffs to the U-Channel as shown, using two 2-56 x 1/4" screws.
 
2 x 2 x

Figure 16.
 
Step 17.
Attach the electronics carrier as shown, using two 2-56 x 1/4" screws.
 
2 x  
 

Figure 17.

Step 18.
To prevent the wires from tangling, you will want to secure them as shown. This can be done with wire ties or similar, not included. Make sure that the ankle servo is positioned as shown when securing the wires to ensure the full range of motion is available.


Figure 18.
 
Step 19.
Attach the power switch to the electronics carrier as shown.


Figure 19.
 
Step 20.
Your battery can be attached with a wire tie or Velcro, not included.

A 6vdc battery will power the robot fine, however, as the battery discharges, the SSC-32 will reset even though there is still sufficient power for the servos. A 7.2vdc battery will lessen this effect, but it is slightly harder on the servos.

For maximum run time, power the VL input from a separate 9vdc battery. Remember to remove the VS=VL jumper to isolate the two supplies. The 6 or 7.2vdc battery is still required!


Figure 20.

For SSC-32 with Visual Sequencer control
 
Step 21.
Install the SSC-32 using four 4-40 x 1/4" screws. Make sure to orient the SSC-32 as shown.
 
4 x  
 

Figure 21.
 
Step 22.
Connect the servos to their appropriate I/O channels on the SSC-32. Consult Table 22, and make sure to check your work.
 
SSC-32 I/O Servo
00 Right Ankle
01 Right Knee
02 Right Hip
16 Left Ankle
17 Left Knee
18 Left Hip

Table 22.


Figure 22.
 
Step 23.
Connect the wiring harness to VS1 or VS2 on the SSC-32 as shown. Note, red is (+) and black is (-).


Figure 23.

Step 24.
If you like, you can flip the SSC-32 around to protect the wires and take up less space.

For controlling this robot with the just the SSC-32 and Sequencer, you need to now move to the Sequencer tutorial.


Figure 24.
 

For SSC-32 with Bot Board (for BASIC program control)
 
Step 25.
If you want to use the Bot Board with the SSC-32, you will need to replace the screws from Step 22 with 3/8" M/F hex standoffs as shown.
 
4 x  
 


Figure 25.
 
Step 26.
Attach the Bot Board as shown using four 4-40 x 1/4" hex socket head cap screws as shown.
 
4 x  
 


Figure 26.

For Bot Board without SSC-32 (for BASIC program control)
(Changed servo connections on 04/01/2008)
 
Step 27.
Install the Bot Board using four 4-40 x 1/4" screws. Make sure to orient the Bot Board as shown. Connect the wiring harness to the VS terminal. Note, red is (+) and black is (-). Connect the servos to their appropriate I/O channels on the Bot Board. Consult Table 28, and make sure to check your work.
 
4 x  
 

Figure 27.
 
Step 28.
If you like, you can flip the Bot Board around to protect the wires and take up less space.
 
Bot Board I/O Servo
4 Left Ankle
5 Left Knee
6 Left Hip
7 Right Ankle
8 Right Knee
10 Right Hip

Table 28.


Figure 28.