systems

Animatronics & Robotics for Film & Television

micromagic

 

B.F. Hexapod (V5) (Developed 2005/8)

 

This hexapod was designed and built after Hitech released there mind blowing robot servo, the HSR-5995TG. This servo promised torque never before seen in a standard size servo, and indeed it did deliver, albeit at a cost! If the servo were run for any length of time at even half the rated torque, they tended to melt! Unfortunately this was discovered after building the V5 hexapod. (This servo has since been superseded with a metal cased version which is supposed to sort out the melting issue.)

 

For this reason V5 was left pretty much untouched until recently when further research was required into the terrain adaptation capabilities of the p.Brain locomotion engine. Although terrain adaptation within the p.Brain software has been tested successfully in the past on the V4 hexapod, it was determined that much better off-road performance could be achieved using an on-board  p.Brain-DS engine and better designed ground contact sensors.

 

Contact Sensors

 

This design utilizes a ball joint at the end of the tibia which is located in a socket within the foot assembly. This gives the foot assembly the three degrees of freedom which are needed to adapt to the shape of the terrain. The footplate at the bottom of the foot assembly is hinged at the front of the foot, and has a micro-switch at the rear which gives the contact signal. The p.Brain only requires an on-off signal, no pressure information is needed. Although this contact sensor arrangement performs extremely well, there are several improvements that could be made on a larger scale assembly.

 

p.Brain-ds 

 

The p.Brain-DS now uses one of the dsPIC33F series processor which was a significant step up from the previous dsPIC30F4011 processor. For the terrain adaptation tests, the p.Brain-DS has been configured to run much more accurate maths routines, as well as data feedback to off-board terminal software. For the additional processing power required, this p.Brain-DS is running at 64Mhz with a refresh rate of 50Hz / 60Hz.

 

Bluetooth control connection

 

The control connection to this Hexapod is through a simple bluetooth serial port via the p.Brain-ds TTL control port. The on-board RS232 port is used for configuring the hexapod geometry / gait and calibration, as well as data feedback to an off-board terminal.

 

 

Future Plans

 

Further development into the ground contact sensor design, although this may be on a larger hexapod.

 

 

Tech Stuff

 

Servos: Hitech HSR-5995TG

Battery: NiMh 4.8V 6500mah

Servo Driver: 1 X p.Brain-DS

CPU: dsPIC33FJ128206 @ 64Mhz

Radio Link: bluetooth

Weight: Aprox 3.3Kg (with battery)

 

 

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