Gripper control

set_gripper_value

description:set gripper angle
parameters: 
1.gripper angle
2.the speed at which the gripper executes running 
returned value:none

set_gripper_state

description:set the opening and closing states of the gripper
parameters: 
1.gripper states: O: open; 1: close
2.the speed at which the gripper executes running 
returned value:none