mirror of
https://github.com/ArduPilot/ardupilot
synced 2025-01-25 18:18:49 -04:00
28cf93d300
This adds (more) correct join rate limiting based on Pauls maths. It avoids the coupling of the axes inherent in the last implementation Pair-Programmed-With: Paul Riseborough <p_riseborough@live.com.au>
268 lines
12 KiB
Python
268 lines
12 KiB
Python
#!/usr/bin/env python
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from aircraft import Aircraft
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import util, time, math
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from math import degrees, radians, cos, sin, tan
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from rotmat import Vector3, Matrix3
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def constrain(value, minv, maxv):
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'''constrain a value to a range'''
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if value < minv:
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value = minv
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if value > maxv:
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value = maxv
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return value
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class Gimbal3Axis(object):
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'''a gimbal simulation'''
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def __init__(self, vehicle):
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# vehicle is the vehicle (usually a multicopter) that the gimbal is attached to
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self.vehicle = vehicle
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# URL of SITL 2nd telem port
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self.mavlink_url = 'tcp:127.0.0.1:5762'
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# rotation matrix (gimbal body -> earth)
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self.dcm = None
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# time of last update
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self.last_update_t = time.time()
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# true angular rate of gimbal in body frame (rad/s)
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self.gimbal_angular_rate = Vector3()
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# observed angular rate (including biases)
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self.gyro = Vector3()
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# joint angles, in radians. in yaw/roll/pitch order. Relative to fwd.
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# So 0,0,0 points forward.
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# Pi/2,0,0 means pointing right
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# 0, Pi/2, 0 means pointing fwd, but rolled 90 degrees to right
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# 0, 0, -Pi/2, means pointing down
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self.joint_angles = Vector3()
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# physical constraints on joint angles in (roll, pitch, azimuth) order
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self.lower_joint_limits = Vector3(radians(-40), radians(-135), radians(-7.5))
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self.upper_joint_limits = Vector3(radians(40), radians(45), radians(7.5))
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self.travelLimitGain = 20
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# true gyro bias
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self.true_gyro_bias = Vector3()
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##################################
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# reporting variables. gimbal pushes these to vehicle code over MAVLink at approx 100Hz
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# reporting rate in Hz
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self.reporting_rate = 100
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# integral of gyro vector over last time interval. In radians
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self.delta_angle = Vector3()
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# integral of accel vector over last time interval. In m/s
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self.delta_velocity = Vector3()
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# we also push joint_angles
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##################################
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# control variables from the vehicle
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# angular rate in rad/s. In body frame of gimbal
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self.demanded_angular_rate = Vector3(radians(0), radians(0), radians(0))
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# gyro bias provided by EKF on vehicle. In rad/s.
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# Should be subtracted from the gyro readings to get true body rotatation rates
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self.supplied_gyro_bias = Vector3()
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###################################
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# communication variables
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self.connection = None
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self.counter = 0
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self.last_report_t = time.time()
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self.last_heartbeat_t = time.time()
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self.seen_heartbeat = False
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self.seen_gimbal_control = False
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self.last_print_t = time.time()
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def update(self):
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'''update the gimbal state'''
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# calculate delta time in seconds
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now = time.time()
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delta_t = now - self.last_update_t
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self.last_update_t = now
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if self.dcm is None:
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# start with copter rotation matrix
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self.dcm = self.vehicle.dcm.copy()
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# 1) Rotate the copters rotation rates into the gimbals frame of reference
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# copterAngRate_G = transpose(DCMgimbal)*DCMcopter*copterAngRate
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copterAngRate_G = self.dcm.transposed()*self.vehicle.dcm*self.vehicle.gyro
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#print("copterAngRate_G ", copterAngRate_G)
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# 2) Subtract the copters body rates to obtain a copter relative rotational
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# rate vector (X,Y,Z) in gimbal sensor frame
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# relativeGimbalRate(X,Y,Z) = gimbalRateDemand - copterAngRate_G
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relativeGimbalRate = self.demanded_angular_rate - copterAngRate_G
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#print("relativeGimbalRate ", relativeGimbalRate)
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# calculate joint angles (euler312 order)
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# calculate copter -> gimbal rotation matrix
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rotmat_copter_gimbal = self.dcm.transposed() * self.vehicle.dcm
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self.joint_angles = Vector3(*rotmat_copter_gimbal.transposed().to_euler312())
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#print("joint_angles ", self.joint_angles)
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# 4) For each of the three joints, calculate upper and lower rate limits
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# from the corresponding angle limits and current joint angles
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#
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# upperRatelimit = (jointAngle - lowerAngleLimit) * travelLimitGain
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# lowerRatelimit = (jointAngle - upperAngleLimit) * travelLimitGain
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#
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# travelLimitGain is equal to the inverse of the bump stop time constant and
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# should be set to something like 20 initially. If set too high it can cause
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# the rates to 'ring' when they the limiter is in force, particularly given
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# we are using a first order numerical integration.
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upperRatelimit = -(self.joint_angles - self.upper_joint_limits) * self.travelLimitGain
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lowerRatelimit = -(self.joint_angles - self.lower_joint_limits) * self.travelLimitGain
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# 5) Calculate the gimbal joint rates (roll, elevation, azimuth)
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#
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# gimbalJointRates(roll, elev, azimuth) = Matrix*relativeGimbalRate(X,Y,Z)
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#
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# where matrix =
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#
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# +- -+
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# | cos(elevAngle), 0, sin(elevAngle) |
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# | |
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# | sin(elevAngle) tan(rollAngle), 1, -cos(elevAngle) tan(rollAngle) |
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# | |
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# | sin(elevAngle) cos(elevAngle) |
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# | - --------------, 0, -------------- |
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# | cos(rollAngle) cos(rollAngle) |
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# +- -+
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rollAngle = self.joint_angles.x
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elevAngle = self.joint_angles.y
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matrix = Matrix3(Vector3(cos(elevAngle), 0, sin(elevAngle)),
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Vector3(sin(elevAngle)*tan(rollAngle), 1, -cos(elevAngle)*tan(rollAngle)),
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Vector3(-sin(elevAngle)/cos(rollAngle), 0, cos(elevAngle)/cos(rollAngle)))
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gimbalJointRates = matrix * relativeGimbalRate
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#print("lowerRatelimit ", lowerRatelimit)
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#print("upperRatelimit ", upperRatelimit)
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#print("gimbalJointRates ", gimbalJointRates)
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# 6) Apply the rate limits from 4)
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gimbalJointRates.x = constrain(gimbalJointRates.x, lowerRatelimit.x, upperRatelimit.x)
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gimbalJointRates.y = constrain(gimbalJointRates.y, lowerRatelimit.y, upperRatelimit.y)
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gimbalJointRates.z = constrain(gimbalJointRates.z, lowerRatelimit.z, upperRatelimit.z)
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# 7) Convert the modified gimbal joint rates to body rates (still copter
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# relative)
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# relativeGimbalRate(X,Y,Z) = Matrix * gimbalJointRates(roll, elev, azimuth)
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#
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# where Matrix =
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#
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# +- -+
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# | cos(elevAngle), 0, -cos(rollAngle) sin(elevAngle) |
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# | |
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# | 0, 1, sin(rollAngle) |
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# | |
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# | sin(elevAngle), 0, cos(elevAngle) cos(rollAngle) |
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# +- -+
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matrix = Matrix3(Vector3(cos(elevAngle), 0, -cos(rollAngle)*sin(elevAngle)),
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Vector3(0, 1, sin(rollAngle)),
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Vector3(sin(elevAngle), 0, cos(elevAngle)*cos(rollAngle)))
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relativeGimbalRate = matrix * gimbalJointRates
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# 8) Add to the result from step 1) to obtain the demanded gimbal body rates
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# in an inertial frame of reference
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# demandedGimbalRatesInertial(X,Y,Z) = relativeGimbalRate(X,Y,Z) + copterAngRate_G
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demandedGimbalRatesInertial = relativeGimbalRate + copterAngRate_G
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#if now - self.last_print_t >= 1.0:
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# print("demandedGimbalRatesInertial ", demandedGimbalRatesInertial)
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# for the moment we will set gyros equal to demanded_angular_rate
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self.gimbal_angular_rate = demandedGimbalRatesInertial + self.true_gyro_bias - self.supplied_gyro_bias
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# update rotation of the gimbal
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self.dcm.rotate(self.gimbal_angular_rate*delta_t)
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self.dcm.normalize()
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# calculate copter -> gimbal rotation matrix
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rotmat_copter_gimbal = self.dcm.transposed() * self.vehicle.dcm
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# calculate joint angles (euler312 order)
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self.joint_angles = Vector3(*rotmat_copter_gimbal.transposed().to_euler312())
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# update observed gyro
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self.gyro = self.gimbal_angular_rate + self.true_gyro_bias
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# update delta_angle (integrate)
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self.delta_angle += self.gyro * delta_t
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# calculate accel in gimbal body frame
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copter_accel_earth = self.vehicle.dcm * self.vehicle.accel_body
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accel = self.dcm.transposed() * copter_accel_earth
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# integrate velocity
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self.delta_velocity += accel * delta_t
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# see if we should do a report
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if now - self.last_report_t >= 1.0 / self.reporting_rate:
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self.send_report()
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self.last_report_t = now
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if now - self.last_print_t >= 1.0:
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self.last_print_t = now
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print('joint_angles ', self.joint_angles)
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def send_report(self):
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'''send a report to the vehicle control code over MAVLink'''
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from pymavlink import mavutil
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if self.connection is None:
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try:
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self.connection = mavutil.mavlink_connection(self.mavlink_url, retries=0)
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except Exception as e:
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return
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print("Gimbal connected to %s" % self.mavlink_url)
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# check for incoming control messages
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while True:
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m = self.connection.recv_match(type=['GIMBAL_CONTROL','HEARTBEAT'], blocking=False)
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if m is None:
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break
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if m.get_type() == 'GIMBAL_CONTROL':
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self.demanded_angular_rate = Vector3(m.demanded_rate_x,
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m.demanded_rate_y,
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m.demanded_rate_z)
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self.supplied_gyro_bias = Vector3(m.gyro_bias_x,
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m.gyro_bias_y,
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m.gyro_bias_z)
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self.seen_gimbal_control = True
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if m.get_type() == 'HEARTBEAT' and not self.seen_heartbeat:
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self.seen_heartbeat = True
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self.connection.mav.srcSystem = m.get_srcSystem()
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self.connection.mav.srcComponent = mavutil.mavlink.MAV_COMP_ID_GIMBAL
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print("Gimbal using srcSystem %u" % self.connection.mav.srcSystem)
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if self.seen_heartbeat:
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now = time.time()
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if now - self.last_heartbeat_t >= 1:
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self.connection.mav.heartbeat_send(mavutil.mavlink.MAV_TYPE_GIMBAL,
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mavutil.mavlink.MAV_AUTOPILOT_ARDUPILOTMEGA,
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0, 0, 0)
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self.last_heartbeat_t = now
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if self.seen_heartbeat:
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self.connection.mav.gimbal_report_send(self.counter,
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self.delta_angle.x,
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self.delta_angle.y,
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self.delta_angle.z,
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self.delta_velocity.x,
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self.delta_velocity.y,
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self.delta_velocity.z,
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self.joint_angles.x,
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self.joint_angles.y,
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self.joint_angles.z)
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self.delta_velocity.zero()
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self.delta_angle.zero()
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self.counter += 1
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