Hello,
I’m using UR5e with Robotiq Hand E gripper attached since a year.
The both the gripper and the robot is completely commissioned.
I was sending the gripper open, close, activate commands from the Python. It was working fine; But, unfortunately the same program is showing the following error.
Traceback (most recent call last):
File gripper.activate()
line 170, in activate if not self.is_active():
line 186, in is_active status = self._get_var(self.STA)
line 109, in _get_var value = int(value_str)
ValueError: invalid literal for int() with base 10: ‘?’
I’m tried many possible ways I’m struck in between. Can some one help with this regards please.
robotiq_gripper.py program
import socket
import threading
import time
from enum import Enum
from typing import Union, Tuple, OrderedDict
class RobotiqGripper:
“”"
Communicates with the gripper directly, via socket with string commands, leveraging string names for variables.
“”"
# WRITE VARIABLES (CAN ALSO READ)
ACT = ‘ACT’ # act : activate (1 while activated, can be reset to clear fault status)
GTO = ‘GTO’ # gto : go to (will perform go to with the actions set in pos, for, spe)
ATR = ‘ATR’ # atr : auto-release (emergency slow move)
ADR = ‘ADR’ # adr : auto-release direction (open(1) or close(0) during auto-release)
FOR = ‘FOR’ # for : force (0-255)
SPE = ‘SPE’ # spe : speed (0-255)
POS = ‘POS’ # pos : position (0-255), 0 = open
# READ VARIABLES
STA = ‘STA’ # status (0 = is reset, 1 = activating, 3 = active)
PRE = ‘PRE’ # position request (echo of last commanded position)
OBJ = ‘OBJ’ # object detection (0 = moving, 1 = outer grip, 2 = inner grip, 3 = no object at rest)
FLT = ‘FLT’ # fault (0=ok, see manual for errors if not zero)
ENCODING = 'UTF-8' # ASCII and UTF-8 both seem to work
class GripperStatus(Enum):
"""Gripper status reported by the gripper. The integer values have to match what the gripper sends."""
RESET = 0
ACTIVATING = 1
# UNUSED = 2 # This value is currently not used by the gripper firmware
ACTIVE = 3
class ObjectStatus(Enum):
"""Object status reported by the gripper. The integer values have to match what the gripper sends."""
MOVING = 0
STOPPED_OUTER_OBJECT = 1
STOPPED_INNER_OBJECT = 2
AT_DEST = 3
def __init__(self):
"""Constructor."""
self.socket = None
self.command_lock = threading.Lock()
self._min_position = 0
self._max_position = 255
self._min_speed = 0
self._max_speed = 255
self._min_force = 0
self._max_force = 255
def connect(self, hostname: str, port: int, socket_timeout: float = 2.0) -> None:
"""Connects to a gripper at the given address.
:param hostname: Hostname or ip.
:param port: Port.
:param socket_timeout: Timeout for blocking socket operations.
"""
self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self.socket.connect((hostname, port))
self.socket.settimeout(socket_timeout)
def disconnect(self) -> None:
"""Closes the connection with the gripper."""
self.socket.close()
def _set_vars(self, var_dict: OrderedDict[str, Union[int, float]]):
"""Sends the appropriate command via socket to set the value of n variables, and waits for its 'ack' response.
:param var_dict: Dictionary of variables to set (variable_name, value).
:return: True on successful reception of ack, false if no ack was received, indicating the set may not
have been effective.
"""
# construct unique command
cmd = "SET"
for variable, value in var_dict.items():
cmd += f" {variable} {str(value)}"
cmd += '\n' # new line is required for the command to finish
# atomic commands send/rcv
with self.command_lock:
self.socket.sendall(cmd.encode(self.ENCODING))
data = self.socket.recv(1024)
return self._is_ack(data)
def _set_var(self, variable: str, value: Union[int, float]):
"""Sends the appropriate command via socket to set the value of a variable, and waits for its 'ack' response.
:param variable: Variable to set.
:param value: Value to set for the variable.
:return: True on successful reception of ack, false if no ack was received, indicating the set may not
have been effective.
"""
return self._set_vars(OrderedDict([(variable, value)]))
def _get_var(self, variable: str):
"""Sends the appropriate command to retrieve the value of a variable from the gripper, blocking until the
response is received or the socket times out.
:param variable: Name of the variable to retrieve.
:return: Value of the variable as integer.
"""
# atomic commands send/rcv
with self.command_lock:
cmd = f"GET {variable}\n"
self.socket.sendall(cmd.encode(self.ENCODING))
data = self.socket.recv(1024)
# expect data of the form 'VAR x', where VAR is an echo of the variable name, and X the value
# note some special variables (like FLT) may send 2 bytes, instead of an integer. We assume integer here
var_name, value_str = data.decode(self.ENCODING).split()
if var_name != variable:
raise ValueError(f"Unexpected response {data} ({data.decode(self.ENCODING)}): does not match '{variable}'")
value = int(value_str)
return value
@staticmethod
def _is_ack(data: str):
return data == b'ack'
def _reset(self):
"""
Reset the gripper.
The following code is executed in the corresponding script function
def rq_reset(gripper_socket="1"):
rq_set_var("ACT", 0, gripper_socket)
rq_set_var("ATR", 0, gripper_socket)
while(not rq_get_var("ACT", 1, gripper_socket) == 0 or not rq_get_var("STA", 1, gripper_socket) == 0):
rq_set_var("ACT", 0, gripper_socket)
rq_set_var("ATR", 0, gripper_socket)
sync()
end
sleep(0.5)
end
"""
self._set_var(self.ACT, 0)
self._set_var(self.ATR, 0)
while (not self._get_var(self.ACT) == 0 or not self._get_var(self.STA) == 0):
self._set_var(self.ACT, 0)
self._set_var(self.ATR, 0)
time.sleep(0.5)
def activate(self, auto_calibrate: bool = True):
"""Resets the activation flag in the gripper, and sets it back to one, clearing previous fault flags.
:param auto_calibrate: Whether to calibrate the minimum and maximum positions based on actual motion.
The following code is executed in the corresponding script function
def rq_activate(gripper_socket="1"):
if (not rq_is_gripper_activated(gripper_socket)):
rq_reset(gripper_socket)
while(not rq_get_var("ACT", 1, gripper_socket) == 0 or not rq_get_var("STA", 1, gripper_socket) == 0):
rq_reset(gripper_socket)
sync()
end
rq_set_var("ACT",1, gripper_socket)
end
end
def rq_activate_and_wait(gripper_socket="1"):
if (not rq_is_gripper_activated(gripper_socket)):
rq_activate(gripper_socket)
sleep(1.0)
while(not rq_get_var("ACT", 1, gripper_socket) == 1 or not rq_get_var("STA", 1, gripper_socket) == 3):
sleep(0.1)
end
sleep(0.5)
end
end
"""
if not self.is_active():
self._reset()
while (not self._get_var(self.ACT) == 0 or not self._get_var(self.STA) == 0):
time.sleep(0.01)
self._set_var(self.ACT, 1)
time.sleep(1.0)
while (not self._get_var(self.ACT) == 1 or not self._get_var(self.STA) == 3):
time.sleep(0.01)
# auto-calibrate position range if desired
if auto_calibrate:
self.auto_calibrate()
def is_active(self):
"""Returns whether the gripper is active."""
status = self._get_var(self.STA)
return RobotiqGripper.GripperStatus(status) == RobotiqGripper.GripperStatus.ACTIVE
def get_min_position(self) -> int:
"""Returns the minimum position the gripper can reach (open position)."""
return self._min_position
def get_max_position(self) -> int:
"""Returns the maximum position the gripper can reach (closed position)."""
return self._max_position
def get_open_position(self) -> int:
"""Returns what is considered the open position for gripper (minimum position value)."""
return self.get_min_position()
def get_closed_position(self) -> int:
"""Returns what is considered the closed position for gripper (maximum position value)."""
return self.get_max_position()
def is_open(self):
"""Returns whether the current position is considered as being fully open."""
return self.get_current_position() <= self.get_open_position()
def is_closed(self):
"""Returns whether the current position is considered as being fully closed."""
return self.get_current_position() >= self.get_closed_position()
def get_current_position(self) -> int:
"""Returns the current position as returned by the physical hardware."""
return self._get_var(self.POS)
def auto_calibrate(self, log: bool = True) -> None:
"""Attempts to calibrate the open and closed positions, by slowly closing and opening the gripper.
:param log: Whether to print the results to log.
"""
# first try to open in case we are holding an object
(position, status) = self.move_and_wait_for_pos(self.get_open_position(), 64, 1)
if RobotiqGripper.ObjectStatus(status) != RobotiqGripper.ObjectStatus.AT_DEST:
raise RuntimeError(f"Calibration failed opening to start: {str(status)}")
# try to close as far as possible, and record the number
(position, status) = self.move_and_wait_for_pos(self.get_closed_position(), 64, 1)
if RobotiqGripper.ObjectStatus(status) != RobotiqGripper.ObjectStatus.AT_DEST:
raise RuntimeError(f"Calibration failed because of an object: {str(status)}")
assert position <= self._max_position
self._max_position = position
# try to open as far as possible, and record the number
(position, status) = self.move_and_wait_for_pos(self.get_open_position(), 64, 1)
if RobotiqGripper.ObjectStatus(status) != RobotiqGripper.ObjectStatus.AT_DEST:
raise RuntimeError(f"Calibration failed because of an object: {str(status)}")
assert position >= self._min_position
self._min_position = position
if log:
print(f"Gripper auto-calibrated to [{self.get_min_position()}, {self.get_max_position()}]")
def move(self, position: int, speed: int, force: int) -> Tuple[bool, int]:
"""Sends commands to start moving towards the given position, with the specified speed and force.
:param position: Position to move to [min_position, max_position]
:param speed: Speed to move at [min_speed, max_speed]
:param force: Force to use [min_force, max_force]
:return: A tuple with a bool indicating whether the action it was successfully sent, and an integer with
the actual position that was requested, after being adjusted to the min/max calibrated range.
"""
def clip_val(min_val, val, max_val):
return max(min_val, min(val, max_val))
clip_pos = clip_val(self._min_position, position, self._max_position)
clip_spe = clip_val(self._min_speed, speed, self._max_speed)
clip_for = clip_val(self._min_force, force, self._max_force)
# moves to the given position with the given speed and force
var_dict = OrderedDict([(self.POS, clip_pos), (self.SPE, clip_spe), (self.FOR, clip_for), (self.GTO, 1)])
return self._set_vars(var_dict), clip_pos
def move_and_wait_for_pos(self, position: int, speed: int, force: int) -> Tuple[int, ObjectStatus]: # noqa
"""Sends commands to start moving towards the given position, with the specified speed and force, and
then waits for the move to complete.
:param position: Position to move to [min_position, max_position]
:param speed: Speed to move at [min_speed, max_speed]
:param force: Force to use [min_force, max_force]
:return: A tuple with an integer representing the last position returned by the gripper after it notified
that the move had completed, a status indicating how the move ended (see ObjectStatus enum for details). Note
that it is possible that the position was not reached, if an object was detected during motion.
"""
set_ok, cmd_pos = self.move(position, speed, force)
if not set_ok:
raise RuntimeError("Failed to set variables for move.")
# wait until the gripper acknowledges that it will try to go to the requested position
while self._get_var(self.PRE) != cmd_pos:
time.sleep(0.001)
# wait until not moving
cur_obj = self._get_var(self.OBJ)
while RobotiqGripper.ObjectStatus(cur_obj) == RobotiqGripper.ObjectStatus.MOVING:
cur_obj = self._get_var(self.OBJ)
# report the actual position and the object status
final_pos = self._get_var(self.POS)
final_obj = cur_obj
return final_pos, RobotiqGripper.ObjectStatus(final_obj)
Gripper movement program
import robotiq_gripper
import time
ip = “192.168.0.100”
def log_info(gripper):
print(f"Pos: {str(gripper.get_current_position()): >3} "
f"Open: {gripper.is_open(): <2} "
f"Closed: {gripper.is_closed(): <2} ")
print(“Creating gripper…”)
gripper = robotiq_gripper.RobotiqGripper()
print(“Connecting to gripper…”)
gripper.connect(ip, 63352)
print(“Activating gripper…”)
gripper.activate()
gripper.move_and_wait_for_pos(255, 255, 255)
log_info(gripper)
gripper.move_and_wait_for_pos(0, 255, 255)
log_info(gripper)
From looking at it briefly i would conclude this:
This tries to convert the variable value_str to an integer.
However value_str is "?" and there is no way to convert a question mark into an integer.
value_str is set to the self.STA attribute of the RobotiqGripper class.
You wrote that this attribute is a part of the “READ VARIABLES” so I am assuming it is part of the regular Roboti API.
This process seems to fail or at least not give the expected value resulting in the question mark.
you should check if using the def _get_var(self, variable: str)function with the other READ VARIABLES produces the same problem or if this is only when checking the STA status.
This will tell you if its a general socket connection problem or something else.