Alan Marconett

From HBRC WIki

LOKI BIPED ROBOT

Loki now has feet with proper overlap (to allow the CG to stay over the foot supporting the 'bot), and a continuous recycle of 5 basic states (gait) allow it to walk. Similar sequences allow turns, and all sequences can be transversed in both directions.

I can currently use the ultrasonic sensor to stop forward walk, and reverse direction. I then realized that I need two sensors (or sensor rotation to detect which way to TURN to avoid an obstacle. So I added the IR sensors.

The battery pack, while it can be secured below the controller board adequately, is still a little to heavy for the S3004 servos, so I leave the battery back connected via a cable.

LOKI NOTES

Cheap walking robot, low cost parts, can be made at home
Loki is inspired by the efforts of David Buckley http://davidbuckley.net/DB/Loki.htm
Original construction was wood (I later found out)
My Loki is constructed of PCB material to a similar size
Currently using four Futaba S3004 R/C servos, need bigger knee servos
Battery is a salvaged 6-cell Ni-MH 7.2v 1300 mAH pack
Controller board is a $15 (bare) “QwikFlash” 18F4620 PIC board available from http://www.picbook.com/
50Mhz, 64K Flash, 3K RAM + EEPROM
Blue Tooth wireless for telemetry and monitor control
EEPROM gaits editable over wireless link.
PIC programming via ICD2
Control program written in Hitech ‘C’, used to develop gaits
Two modes, autonomous and control via a small monitor program
Parser used to decode commands received by monitor
EEPROM commands save, view and execute steps in sequences
Autonomous control currently consists of simple obstacle avoidance while doing a simple walk.
Sensors include two Sharp GP2D12 IR range finders and a SRF08 Ultrasonic Range finder
Body and feet PCB material CAD designed and cut on my CNC’d Sherline mill
Loki’s gait is exaggerated due to the need to clear the toes of the overlapping feet
R/C servos are driven by two timers and interrupts in the PIC
Servo commands set new angle for servo, and time to get to new position
Gaits are stored by strings of servo move commands, similar to those of the SSC32 (LM) servo controller.
To walk, a simple array of 6 strings is repeated in an endless loop.
More strings allow Loki to make turns.
An FSM (Finite State Machine) selects the strings to be used, and changes the string selection upon recognition of an object by a sensor.