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delete the useless file
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tiboy
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#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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"""Force control with the Kuka robot where the goal is to follow a moving sphere and contact with the table.
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"""
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# Reference :
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# [1] A Tutorial Survey and Comparison of Impedance Control on Robotic Manipulation
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# this is for my pc because some setting issues
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import sys
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sys.path.remove('/opt/ros/kinetic/lib/python2.7/dist-packages')
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import numpy as np
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from itertools import count
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from pyrobolearn.simulators import Bullet
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from pyrobolearn.worlds import BasicWorld
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from pyrobolearn.robots import KukaIIWA, Body, sensors
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from pyrobolearn.utils.transformation import *
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import matplotlib.pyplot as plt
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# The sphere is used to visualize the reference trajectory, So I creat the sphere trajectory as the reference
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def manipulation(world, robot, sphere, FT_sensor):
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# First step is to arrive the initial position
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for t in count():
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# move sphere
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sphere.position = np.array([0.33, 0, 0.8])
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# get current end-effector position and velocity in the task/operational space
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x = robot.get_link_world_positions(link_id)
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dx = robot.get_link_world_linear_velocities(link_id)
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o = robot.get_link_world_orientations(link_id)
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do = robot.get_link_world_angular_velocities(link_id)
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# Get joint positions
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q = robot.get_joint_positions()
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# Get linear jacobian
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if robot.has_floating_base():
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J = robot.get_jacobian(link_id, q=q)[:, qIdx + 6]
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else:
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J = robot.get_jacobian(link_id, q=q)[:, qIdx]
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# Pseudo-inverse: \hat{J} = J^T (JJ^T + k^2 I)^{-1}
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Jp = robot.get_damped_least_squares_inverse(J, damping)
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dv = kp * (sphere.position - x) - kd * dx
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dw = kp * quaternion_error(sphere.orientation, o) - kd * do
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# evaluate damped-least-squares IK
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dq = Jp.dot(np.hstack((dv, dw)))
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# set joint positions
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q = q[qIdx] + dq * dt
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robot.set_joint_positions(q, joint_ids=joint_ids)
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# after 300 steps, continue to next phase
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if t > 300:
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break
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# step in simulation
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world.step(sleep_dt=dt)
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# this process is to approach to the face of table
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for t in count():
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Fz_desired = 10
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# move sphere
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sphere.position = np.array([0.33, 0, 0.8-0.0005*t])
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# get current end-effector position and velocity in the task/operational space
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x = robot.get_link_world_positions(link_id)
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dx = robot.get_link_world_linear_velocities(link_id)
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o = robot.get_link_world_orientations(link_id)
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do = robot.get_link_world_angular_velocities(link_id)
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# Get joint positions
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q = robot.get_joint_positions()
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# Get linear jacobian
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if robot.has_floating_base():
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J = robot.get_jacobian(link_id, q=q)[:, qIdx + 6]
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else:
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J = robot.get_jacobian(link_id, q=q)[:, qIdx]
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# Pseudo-inverse: \hat{J} = J^T (JJ^T + k^2 I)^{-1}
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Jp = robot.get_damped_least_squares_inverse(J, damping)
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dv = kp * (sphere.position - x) - kd * dx
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dw = kp * quaternion_error(sphere.orientation, o) - kd * do
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# evaluate damped-least-squares IK
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dq = Jp.dot(np.hstack((dv, dw)))
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# set joint positions
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# robot.set_joint_velocities(dq, joint_ids=joint_ids)
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q = q[qIdx] + dq * dt
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robot.set_joint_positions(q, joint_ids=joint_ids)
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if FT_sensor.sense() is not None:
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# condition to the next phase
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if FT_sensor.sense()[2] > Fz_desired:
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break
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# step in simulation
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world.step(sleep_dt=dt)
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# initial some necessary parameters
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Fz_error_old = 0 # used in PI
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sp_z = []
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num = [] # used to plot the figure
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force_z = [] # store the current force
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force_z_desired = [] # store the desired force
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if flag == 1:
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detx = np.array([0.0, 0.0, 0.0])
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# force control phase
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for t in count():
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Fz_desired = 100 # set the desire force 100N
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# move sphere
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if t == 0:
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z = robot.get_link_world_positions(link_id)[2]
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sphere.position = np.array([0.38 - r * np.sin(w * t + np.pi / 2), r * np.cos(w * t + np.pi / 2), z])
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# zz = z - 0.002 # Try to make the end-effector touch the surface of the table
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# get current end-effector position and velocity in the task/operational space
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x = robot.get_link_world_positions(link_id)
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dx = robot.get_link_world_linear_velocities(link_id)
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o = robot.get_link_world_orientations(link_id)
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do = robot.get_link_world_angular_velocities(link_id)
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# Get joint positions
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q = robot.get_joint_positions()
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# Get linear jacobian
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if robot.has_floating_base():
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J = robot.get_jacobian(link_id, q=q)[:, qIdx + 6]
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else:
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J = robot.get_jacobian(link_id, q=q)[:, qIdx]
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# Pseudo-inverse: \hat{J} = J^T (JJ^T + k^2 I)^{-1}
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Jp = robot.get_damped_least_squares_inverse(J, damping)
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# Apply the admittance control
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Fz_current = FT_sensor.sense()[2] # record the current Fz
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force_z.append(Fz_current)
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force_z_desired.append(Fz_desired)
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Fz_error = Fz_current - Fz_desired # record the current error
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# flag == 0 PI(force feedback to adjust x)
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# flag ==1 (admittance control)
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if flag == 0:
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Fz_error_integral = Fz_error + Fz_error_old
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zzz = sphere.position[2] + 0.0000001 * Fz_error + 0.000002 * Fz_error_integral
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Fz_error_old = Fz_error # record the current error as the old error
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elif flag == 1:
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# the equation is demonstrated in reference [1] eq(33)
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M = 1
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D = 2000
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K = 800000
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numerator = Fz_error * np.square(dt) + D * dt * detx[1] + M * (2 * detx[1] - detx[2])
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denominator = M + D*dt + K*np.square(dt)
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detx_ = numerator / denominator
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detx[2] = detx[1]
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detx[1] = detx[0]
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detx[0] = detx_
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zzz = sphere.position[2] + detx[0]
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# keep a circle trajectory
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sphere.position = np.array([0.38 - r * np.sin(w * t + np.pi / 2), r * np.cos(w * t + np.pi / 2), zzz])
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dv = kp * (sphere.position - x) - kd * dx # compute the other direction tracking error term
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num.append(t)
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dw = kp * quaternion_error(sphere.orientation, o) - kd * do
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# evaluate damped-least-squares IK
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dq = Jp.dot(np.hstack((dv, dw)))
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# set joint positions
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q = q[qIdx] + dq * dt
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robot.set_joint_positions(q, joint_ids=joint_ids)
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print(Fz_error, dv[2])
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if t == 800:
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break
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# step in simulation
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world.step(sleep_dt=dt)
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# plt.plot(num, sp_z)
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plt.plot(num, force_z, 'b')
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plt.plot(num, force_z_desired, '--r')
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plt.show()
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if __name__=='__main__':
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# Create simulator
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sim = Bullet()
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# create world
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world = BasicWorld(sim)
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# flag : 0 # PI control
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flag = 0
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# create robot
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robot = KukaIIWA(sim)
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robot.print_info()
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world.load_robot(robot)
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world.load_table(position=np.array([1, 0., 0.]), orientation=np.array([0.0, 0.0, 0.0, 1.0]))
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# define useful variables for IK
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dt = 1. / 240
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link_id = robot.get_end_effector_ids(end_effector=0)
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joint_ids = robot.joints # actuated joint
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damping = 0.01 # for damped-least-squares IK
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wrt_link_id = -1 # robot.get_link_ids('iiwa_link_1')
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qIdx = robot.get_q_indices(joint_ids)
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# define gains
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kp = 500 # 5 if velocity control, 50 if position control
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kd = 5 # 2*np.sqrt(kp)
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# create sphere to follow
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sphere = world.load_visual_sphere(position=np.array([0.5, 0., 0.5]), radius=0.05, color=(1, 0, 0, 0.5))
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sphere = Body(sim, body_id=sphere)
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# set initial joint p
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# ositions (based on the position of the sphere at [0.5, 0, 1])
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robot.reset_joint_states(q=[8.84305270e-05, 7.11378917e-02, -1.68059886e-04, -9.71690439e-01, 1.68308810e-05,
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3.71467111e-01, 5.62890805e-05])
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# define amplitude and angular velocity when moving the sphere
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w = 0.01
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r = 0.05
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# I set the reference orientation to a constant
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sphere.orientation = np.array([1, 0, 0, 0])
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FT_sensor = sensors.JointForceTorqueSensor(sim, body_id=robot.id, joint_ids=6)
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manipulation(world, robot, sphere, FT_sensor)
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