if (sim_call_type==sim_childscriptcall_initialization) then 
	steer_handle= simGetObjectHandle('steer_joint')
	motor_handle= simGetObjectHandle('motor_joint')
	fl_brake_handle= simGetObjectHandle('fl_brake_joint')
	fr_brake_handle= simGetObjectHandle('fr_brake_joint')
	bl_brake_handle= simGetObjectHandle('bl_brake_joint')
	br_brake_handle= simGetObjectHandle('br_brake_joint')
	
	--wheel radius:         0.09
	--wheel base:             0.6
	--wheel track:             0.35
	--maximum steering rate:     70 deg/sec
	
		--the maximum steer angle 30 degree
	max_steer_angle=0.5235987
		--the maximum torque of the motor
	motor_torque=60
	
	dVel=1
	dSteer=0.1
	
		--input steer
	steer_angle=0
		--input velocity
	motor_velocity=dVel*10
		--input brake
	brake_force=0
end 

if (sim_call_type==sim_childscriptcall_cleanup) then 
 
end 

if (sim_call_type==sim_childscriptcall_actuation) then 
	--current steer pos
	steer_pos=simGetJointPosition(steer_handle);
	--current angular velocity of back left wheel
	bl_wheel_velocity=simGetObjectFloatParameter(bl_brake_handle,2012)
	--current angular velocity of back right wheel
	br_wheel_velocity=simGetObjectFloatParameter(br_brake_handle,2012)
	--average angular velocity of the back wheels
	rear_wheel_velocity=(bl_wheel_velocity+br_wheel_velocity)/2
	--linear velocity
	linear_velocity=rear_wheel_velocity*0.09 
	
	
	-- Read the keyboard messages (make sure the focus is on the main window, scene view):
	message,auxiliaryData=simGetSimulatorMessage()

	while message~=-1 do
		if (message==sim_message_keypress) then

			Msg="Tecla: "
            		Msg=Msg..auxiliaryData[1]
			simAddStatusbarMessage(Msg)

			if (auxiliaryData[1]==2007) then
				-- up key
				if (motor_velocity<dVel*9.99) then
					motor_velocity=motor_velocity+dVel
				end
			end
			if (auxiliaryData[1]==2008) then
				-- down key
				if (motor_velocity>-dVel*1.99) then
					motor_velocity=motor_velocity-dVel
				else
				--	brake_force=100
				end
			end
			if (auxiliaryData[1]==2009) then
				-- left key
				if (steer_angle<dSteer*4.99) then
					steer_angle=steer_angle+dSteer
				end
			end
			if (auxiliaryData[1]==2010) then
				-- right key
				if (steer_angle>-dSteer*4.99) then
					steer_angle=steer_angle-dSteer
				end
			end
            if (auxiliaryData[1]==115) then
				-- s key
				motor_velocity=0.0
			end
		end
		message,auxiliaryData=simGetSimulatorMessage()
	end
	
	if (math.abs(motor_velocity)<dVel*0.1) then
		brake_force=100
	else
		brake_force=0
	end
	
		--set maximum steer angle
	if (steer_angle> max_steer_angle) then
	steer_angle=max_steer_angle
	end
	if (steer_angle< -max_steer_angle) then
	steer_angle= -max_steer_angle
	end
	simSetJointTargetPosition(steer_handle, steer_angle)
	
		--brake and motor can not be applied at the same time
	if(brake_force>0) then
	simSetJointForce(motor_handle, 0)
	else
	simSetJointForce(motor_handle, motor_torque)
	simSetJointTargetVelocity(motor_handle, motor_velocity)
	end
	
	simSetJointForce(fr_brake_handle, brake_force)
	simSetJointForce(fl_brake_handle, brake_force)
	simSetJointForce(bl_brake_handle, brake_force)
	simSetJointForce(br_brake_handle, brake_force)
end