#a mimic joint can act as a gear between two joints
#you can control the gear ratio in magnitude and sign (>0 reverses direction)

import pybullet as p
import time
p.connect(p.GUI)
p.loadURDF("plane.urdf",0,0,-2)
wheelA = p.loadURDF("differential/diff_ring.urdf",[0,0,0])
for i in range(p.getNumJoints(wheelA)):
	print(p.getJointInfo(wheelA,i))
	p.setJointMotorControl2(wheelA,i,p.VELOCITY_CONTROL,targetVelocity=0,force=0)


c = p.createConstraint(wheelA,1,wheelA,3,jointType=p.JOINT_GEAR,jointAxis =[0,1,0],parentFramePosition=[0,0,0],childFramePosition=[0,0,0])
p.changeConstraint(c,gearRatio=1, maxForce=10000)

c = p.createConstraint(wheelA,2,wheelA,4,jointType=p.JOINT_GEAR,jointAxis =[0,1,0],parentFramePosition=[0,0,0],childFramePosition=[0,0,0])
p.changeConstraint(c,gearRatio=-1, maxForce=10000)

c = p.createConstraint(wheelA,1,wheelA,4,jointType=p.JOINT_GEAR,jointAxis =[0,1,0],parentFramePosition=[0,0,0],childFramePosition=[0,0,0])
p.changeConstraint(c,gearRatio=-1, maxForce=10000)


p.setRealTimeSimulation(1)
while(1):
	time.sleep(0.01)
#p.removeConstraint(c)