The two legged reverse knee walker project:
I decided to use a Lynxmotion Biped Scout kit and try out some cheap Hongkong servos MG995 which are widely known and available for about 10-20USD. These servos have metal gears (good) but tend to jitter because of bad electronics or analogue pot.
Anyway, this project should realize an autonomous biped walker with reverse knees.
Her are two videos of my Biped Scout with (jittering cheap) servos detecting and avoiding walls by use of a SHARP GP12 sensor on a pan head micro servo.
plus a power sensing to go to sleep when power is running short.
Microcontroller board was an Atom Bot Board II
Servo Controller is a Lynxmotion SSC-32
Description of what you will see:
The Biped Scout starts with a sleep (sitting home position) position and then stands up for walking.
(He looks downwards, this could be used to detect gaps, stairs or smaller obstacles. Better would be a second SHARP sensor directed towards the floor)
If the Sharp distance sensor detects an obstacle, the robot stops his walking movement and
turns the Sharp sensor 45° to the left and to the right to check in which direction the distance to the wall is larger (more save to go there..).
Then he turns hisself 45° towards this direction and makes at lest one step forward.
This procedure continues until he does no longer detect a wall in front of him.
At the end he is programmed to demonstrate, what he does when the battery is low –
he stops his current walking cycle and goes down to sleep position.
here some more images:
(to protect the electronics from being damaged by falling backwards I have added two aluminium bumpers, the battery is situated in the lower front chest for better balance)
Battery sensing has been done this way:
Here is a program description and the program.bas file:
This program is an example for a movement presentation of the Biped Scout Robot with TowerPro MG995 Servos, SSC-32 and Atom Bot Board
with Atom PRO 24 pin processor.
There is a cable from SSC-32 (any unused servo pin) to the Atom Board PIN 3, this cable makes the Atom aware of
the power supply of the SSC-32 servos and he can detect if power goes down and by this prevent the Robot from falling.
See the power cable image in this folder
The Steps Wordtable was created with the Lynxmotion Sequencer SEQ-01
The following Sequences are possible:
0 home position
2 sleep position
3 to step left
4 to step right
5 step left
6 step right
7 step back left
8 step back rigth
9 from left to home
10 from right to home
11 turn 45° right
12 turn 45° left
13 standup slowly
After uploding the program, the robot goes down to a sleep position.
When you press button 5 (green led), a countdown starts and he checks on PIN 3 if his batterie has enough power.
(Therefore a cable goes from PIN 3 to one of the Servopins of the SSC-32 Board. –>batteriesensor.jpg)
If he has enough power the robot stands up slowly, makes a bow, and lifts his right leg.
Otherwhise he announces it with a beep.
In the main loop step right alternates with step left.
If the Sharp distance sensor detects a wall closer than 20cm the sensor is panned 45° to the left and to the right.
He detects in which direction the distance is larger (no or farther away obstacle)
He makes a 45° turn towards this (safer) direction, then makes on step.
He continues until he observes no longer an obstacle in front of him.