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added feedforward control inputs force and torque

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This commit is contained in:
Yifei Simon Shao
2023-06-11 10:12:50 -04:00
parent f2c544d7b9
commit 2aa5894abc
3 changed files with 104 additions and 1 deletions
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99
rotorpy/controllers/quadrotor_control.py
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@@ -63,6 +63,105 @@ class SE3Control(object):
self.f_to_TM = np.vstack((np.ones((1,self.num_rotors)),np.hstack([np.cross(self.rotor_pos[key],np.array([0,0,1])).reshape(-1,1)[0:2] for key in self.rotor_pos]), np.array([k*(-1)**i for i in range(self.num_rotors)]).reshape(1,-1)))
self.TM_to_f = np.linalg.inv(self.f_to_TM)
def update_ref(self, t, flat_output):
"""
This function receives the current time, and desired flat
outputs. It returns the reference command inputs.
Follows https://repository.upenn.edu/edissertations/547/
Inputs:
t, present time in seconds
flat_output, a dict describing the present desired flat outputs with keys
x, position, m
x_dot, velocity, m/s
x_ddot, acceleration, m/s**2 a
x_dddot, jerk, m/s**3 a_dot
x_ddddot, snap, m/s**4 a_ddot
yaw, yaw angle, rad
yaw_dot, yaw rate, rad/s
yaw_ddot, yaw acceleration, rad/s**2 #required! not the same if computing command using controller
Outputs:
control_input, a dict describing the present computed control inputs with keys
cmd_motor_speeds, rad/s
cmd_thrust, N (for debugging and laboratory; not used by simulator)
cmd_moment, N*m (for debugging; not used by simulator)
cmd_q, quaternion [i,j,k,w] (for laboratory; not used by simulator)
cmd_w, angular velocity
cmd_a, angular acceleration
"""
cmd_motor_speeds = np.zeros((4,))
cmd_q = np.zeros((4,))
def normalize(x):
"""Return normalized vector."""
return x / np.linalg.norm(x)
# def vee_map(S):
# """Return vector corresponding to given skew symmetric matrix."""
# return np.array([-S[1,2], S[0,2], -S[0,1]])
# Desired force vector.
t = flat_output['x_ddot']+ np.array([0, 0, self.g])
b3 = normalize(t)
F_des = self.mass * (t)# this is vectorized
# Desired thrust is force projects onto b3 axis.
# R = Rotation.from_quat(state['q']).as_matrix() #this is where most of the problem is, there is no error in rotation!
# b3 = R @ np.array([0, 0, 1])
u1 = np.dot(F_des, b3)
# Desired orientation to obtain force vector.
b3_des = normalize(F_des) #b3_des and b3 are the same
yaw_des = flat_output['yaw']
c1_des = np.array([np.cos(yaw_des), np.sin(yaw_des), 0])
b2_des = normalize(np.cross(b3_des, c1_des))
b1_des = np.cross(b2_des, b3_des)
R_des = np.stack([b1_des, b2_des, b3_des]).T
R = R_des# assume we have perfect tracking on rotation
# Orientation error.
# S_err = 0.5 * (R_des.T @ R - R.T @ R_des)
# att_err = vee_map(S_err)
# Following section follows Mellinger paper to compute reference angular velocity
dot_u1 = np.dot(b3,flat_output['x_dddot'])
hw = self.mass/u1*(flat_output['x_dddot']-dot_u1*b3)
p = np.dot(-hw, b2_des)
q = np.dot(hw, b1_des)
w_des = np.array([0, 0, flat_output['yaw_dot']])
r = np.dot(w_des, b3_des)
Omega = np.array([p, q, r])
wwu1b3 = np.cross(Omega, np.cross(Omega, u1*b3))
ddot_u1 = np.dot(b3, self.mass*flat_output['x_ddddot']) - np.dot(b3, wwu1b3)
ha = 1.0/u1*(self.mass*flat_output['x_ddddot'] - ddot_u1*b3 - 2*np.cross(Omega,dot_u1*b3) - wwu1b3)
p_dot = np.dot(-ha, b2_des)
q_dot = np.dot(ha, b1_des)
np.cross(Omega, Omega)
r_dot = flat_output['yaw_ddot'] *np.dot(np.array([0,0,1.0]), b3_des) #uniquely need yaw_ddot
Alpha = np.array([p_dot, q_dot, r_dot])
u2 = self.inertia @ Alpha + np.cross(Omega, self.inertia @ Omega)
# print(u1,u2)
TM = np.array([u1, u2[0], u2[1], u2[2]])
cmd_motor_forces = self.TM_to_f @ TM
cmd_motor_speeds = cmd_motor_forces / self.k_eta
cmd_motor_speeds = np.sign(cmd_motor_speeds) * np.sqrt(np.abs(cmd_motor_speeds))
cmd_q = Rotation.from_matrix(R_des).as_quat()
control_input = {'cmd_motor_speeds':cmd_motor_speeds,
'cmd_thrust':u1,
'cmd_moment':u2,
'cmd_q':cmd_q,
'cmd_w':Omega,
'cmd_a':Alpha}
return control_input
def update(self, t, state, flat_output):
"""
This function receives the current time, true state, and desired flat

1
rotorpy/simulate.py
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@@ -98,6 +98,7 @@ def simulate(world, initial_state, vehicle, controller, trajectory, wind_profile
control = [sanitize_control_dic(controller.update(time[-1], mocap_measurements[-1], flat[-1]))]
else:
control = [sanitize_control_dic(controller.update(time[-1], state[-1], flat[-1]))]
control_ref = [sanitize_control_dic(controller.update_ref(time[-1], flat[-1]))]
state_dot = vehicle.statedot(state[0], control[0]['cmd_motor_speeds'], t_step)
imu_measurements.append(imu.measurement(state[-1], state_dot, with_noise=True))
imu_gt.append(imu.measurement(state[-1], state_dot, with_noise=False))

5
rotorpy/trajectories/circular_traj.py
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@@ -113,12 +113,15 @@ class CircularTraj(object):
if self.yaw_bool:
yaw = np.pi/4*np.sin(np.pi*t)
yaw_dot = np.pi*np.pi/4*np.cos(np.pi*t)
yaw_ddot = -np.pi*np.pi*np.pi/4*np.sin(np.pi*t)
else:
yaw = 0
yaw_dot = 0
yaw_ddot = 0
flat_output = { 'x':x, 'x_dot':x_dot, 'x_ddot':x_ddot, 'x_dddot':x_dddot, 'x_ddddot':x_ddddot,
'yaw':yaw, 'yaw_dot':yaw_dot}
'yaw':yaw, 'yaw_dot':yaw_dot, 'yaw_ddot':yaw_ddot}
return flat_output
class ThreeDCircularTraj(object):