How to get the actual kinematic parameters after kinematics calibration?

Introduction

We added kinematics calibration to our newer product, the actual kinematic parameters will be a little different from the nominal DH parameters we provide. The results from get_forward_kinematics() API and Studio have already taken the calibration into account.

Robot Arm Model	Kinematics Calibration
xArm1303 or lower version	No
xArm1304 or Lite6	Please share the SN to the Support Team
xArm1305 or 850	Yes

Python Script

gen_kinematics_params.py

import os
import sys
import socket
import struct

try:
    from yaml import dump
except:
    def dump(data, f, indent=0, **kwargs):
        buf = []
        for key, val in data.items():
            if isinstance(val, dict):
                buf.append('{}{}:'.format(' ' * indent, key))
                buf += dump(val, None, indent=indent+2, **kwargs)
            else:
                buf.append('{}{}: {}'.format(' ' * indent, key, val))
        if f is not None:
            f.write('\n'.join(buf))
        return buf

if __name__ == '__main__':
    if len(sys.argv) < 3:
        print('Usage: {} {{robot_ip}} {{kinematics_suffix (to distinguish your multiple arms)}}'.format(sys.argv[0]))
        exit(1)
    robot_ip = sys.argv[1]
    kinematics_suffix = sys.argv[2]
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect((robot_ip, 502))

    send_data = [0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x08]
    sock.send(bytes(send_data))
    recv_data = sock.recv(179)
    if len(recv_data) == 179 and recv_data[8]:
        robot_dof = recv_data[9]
        robot_type = recv_data[10]
        robot_name = 'uf850' if robot_dof == 6 and robot_type == 12 else 'lite6' if robot_dof == 6 and robot_type == 9 else 'xarm{}'.format(robot_dof)
        ouput_dir = os.path.join(os.path.dirname(__file__), 'user')
        if not os.path.exists(ouput_dir):
            os.makedirs(ouput_dir)
        output_file = os.path.join(ouput_dir, '{}_kinematics_{}.yaml'.format(robot_name, kinematics_suffix))
        params = struct.unpack('<42f', recv_data[11:])
        kinematics = {}
        data = {'kinematics': kinematics}
        for i in range(robot_dof):
            joint_param = {}
            kinematics['joint{}'.format(i + 1)] = joint_param
            joint_param['x'] = params[i * 6]
            joint_param['y'] = params[i * 6 + 1]
            joint_param['z'] = params[i * 6 + 2]
            joint_param['roll'] = params[i * 6 + 3]
            joint_param['pitch'] = params[i * 6 + 4]
            joint_param['yaw'] = params[i * 6 + 5]
        with open(output_file, 'w', encoding='utf-8') as f:
            try:
                dump(data, f, default_flow_style=False, allow_unicode=True, sort_keys=False)
            except:
                dump(data, f, default_flow_style=False, allow_unicode=True)
        print('[Success] save to {}'.format(output_file))
    else:
        print('[Failed] recv_len={}, valid={}'.format(len(recv_data), 0 if len(recv_data) < 9 else recv_data[8]))

Generation of Kinematics parameter file

python gen_kinematics_params.py [robot_ip] [kinematics_suffix]

python gen_kinematics_params.py 192.168.1.212 ip212

• robot_ip represents the IP of the robot arm. You need to connect to the robot arm to obtain the actual parameters.
• kinematics_suffix represents the suffix of the generated parameter file. If successful, the configuration file will be generated in the /user directory. If kinematics_suffix is AAA, then the corresponding file name is as follows
  • xarm5: user/xarm5_kinematics_AAA.yaml
  • xarm6: user/xarm6_kinematics_AAA.yaml
  • xarm7: user/xarm7_kinematics_AAA.yaml
  • lite6: user/lite6_kinematics_AAA.yaml
  • uf850: user/uf850_kinematics_AAA.yaml
• the form will not be DH any more, it is the 6DOF (x,y,z, roll pitch yaw) transformation relationship between adjacent joint coordinates, and the unit is in Meters and Radians.