ABR_Jaco2: Low-level force control interface for the Kinova Jaco2 with torque sensors
ABR_Jaco2 depends on the ABR_Control repo. The repo can be found at https://github.com/abr/abr_control with install instructions in the README.
Additionally, ABR_Jaco2 library depends on Numpy, Sympy, CloudPickle, Matplotlib, and Scipy, and we recommend that you install these libraries before ABR_Jaco2. If you're not sure how to do this, we recommend using Anaconda. Note that installing in a clean environment will require compiling of the dependent libraries, and will take a few minutes.
To install ABR_Jaco2, clone this repository and run:
pip install -e . --no-use-pep517 python setup.py develop
ABR_Jaco2 is tested to work on Python 3.4+.
The ABR_Jaco2 repo is comprised of an interface to communicate with the Kinova Jaco2, and a configuration file for use with the ABR_Control library. This uses Kinova's low level C API to allow for direct force control of the torques being applied by each motor, as well as position control.
1) The interface class provided here communicates with the arm through the low level RS485 API provided by Kinova. With this interface, a control mode can be selected (either position or force), and then target angles or joint torques can be sent to the arm.
NOTE: When using force control mode the control signal must be sent at a frequency faster that 200ms, otherwise the arm will revert to position mode.
2) All of the required information about an arm model is kept in that arm's config file. More information on the formatting of the config can be found in the ABR_Control repo's README. Here we provide a configuration file for the physical Kinova Jaco2 (as opposed to the VREP and Mujoco model config file provided in the ABR_Control repo), based off of SolidWorks CAD files and empirical tuning.
3) The ABR_Control library provides implementations of controllers and path planners that can be used on the Jaco2, with examples provided in this repo.
A script for basic control of the Jaco2 looks like:
import abr_jaco2
from abr_control.controllers import OSC
robot_config = abr_jaco2.Config()
interface = abr_jaco2.Interface(robot_config)
ctrlr = OSC(robot_config)
# instantiate things to avoid creating 200ms delay in main loop
zeros = np.zeros(robot_config.N_LINKS)
ctrlr.generate(q=zeros, dq=zeros, target=zeros(3))
# run once outside main loop as well, returns the cartesian
# coordinates of the end effector
robot_config.Tx('EE', q=zeros)
interface.connect()
interface.init_position_mode()
interface.send_target_angles(robot_config.INIT_TORQUE_POSITION)
target_xyz = [.57, .03 .87] # (x, y, z) target (metres)
interface.init_force_mode()
while 1:
# returns a dictionary with q, dq
feedback = interface.get_feedback()
# ee position
xyz = robot_config.Tx('EE', q=q, target_pos = target_xyz)
u = ctrlr.generate(feedback['q'], feedback['dq'], target_xyz)
interface.send_forces(u, dtype='float32')
error = np.sqrt(np.sum((xyz - TARGET_XYZ[ii])**2))
if error < 0.02:
break
# switch back to position mode to move home and disconnect
interface.init_position_mode()
interface.send_target_angles(robot_config.INIT_TORQUE_POSITION)
interface.disconnect()
The ABR_Jaco2 repo comes with several examples that demonstrate the use of the different controllers. To run simulations of the Jaco2 in VREP or Mujoco, please see the ABR_Control repo.