Blocking and Slow "set_gripper_position" with "wait=False"

xArm/850 Troubleshooting
1

Using the xArm gripper on the xArm 6. Using the 2.5.109 software version and 2.5.5 firmware.

When I call the “set_gripper_position” function with “wait=False” in a loop, the expected behavior is to almost immediately exit, since the wait=False should be non-blocking similar to what happens in the “set_position” command. However, not only is the command blocking, but it takes some time, so that the gripper motion is blocky rather than smooth.

I tried to do the same with blockly, and did not encounter this issue.

2

We need more information to figure out this issue. Could you please share the python codes and Blockly project here, or send me a Email with those files, my Email daniel.wang@ufactory.cc

Here is the Python codes and Blockly I test

import time
from xarm.wrapper import XArmAPI
arm = XArmAPI('192.168.1.83')


arm.set_mode(0)
arm.set_state(0)
time.sleep(1)


position_list=[
[300,-100,100,180,0,0],
[300,-100,300,180,0,0],
[300,100,300,180,0,0],
[300,100,100,180,0,0]
]

for i in range(5):
    for pos in position_list:
        print(pos)
        arm.set_position(*pos,speed=200,wait=False)
    arm.set_gripper_position(pos=800,speed=1000,wait=False)
    for pos in position_list:
        print(pos)
        arm.set_position(*pos,speed=200,wait=False)
    arm.set_gripper_position(pos=0,speed=1000,wait=False)

image
image1605×884 155 KB

3

Here is python code to reproduce the bug:

import time
from xarm.wrapper import XArmAPI
arm = XArmAPI("192.168.1.237")

arm.set_mode(0)
arm.set_state(0)
time.sleep(1)

t0 = time.time()
for i in range(5):
    arm.set_gripper_position(pos=800, speed=1000, wait=False)
    arm.set_gripper_position(pos=0, speed=1000, wait=False)
print(f"Time for 10x set_gripper_position time with wait=False: {time.time() - t0: .2f} [s]")

t0 = time.time()
for i in range(5):
    arm.set_position(x=360, wait=False)
    arm.set_position(x=330, wait=False)
print(f"Time for 10x set_position with wait=False: {time.time() - t0: .2f} [s]")

I’d expect both printed times to be close to zero, since wait=False should be non-blocking. In practice, the set_position works fine, but the set_gripper_position has a bug, since it blocks until the movement is complete:

SDK_VERSION: 1.14.8
ROBOT_IP: 192.168.1.237, VERSION: v2.5.5, PROTOCOL: V1, DETAIL: 6,6,XI1200,XX0000,v2.5.5, TYPE1300: [0, 0]
change protocol identifier to 3
[set_state], xArm is ready to move
Time for 10x set_gripper_position time with wait=False:  4.73 [s]
Time for 10x set_position with wait=False:  0.01 [s]
4

Try to change the “wait” to “wait_motion”, like that.

arm.set_gripper_position(pos=800, speed=1000, wait_motion=False)
5

Changing to wait_motion=False in the code I attached indeed removes the blocking issue, but the gripper doesn’t actually open or close, so this is not a solution.

For reference I’m using the xArm-Python-SDK from pypi with version 1.14.8.

6

The robot has motion planning, it will plan the path if it receive 10 commands at same time.
The gripper does not have the concept of motion planning, it’s a bit like the “servo_j” of the robot, it only execute the last command when it receives 10 commands at same time.
How do you want use the gripper?