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SITL: added gimbal simulator class

mission-4.1.18
Andrew Tridgell 10 years ago
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7f5b206c55
2 changed files with 399 additions and 0 deletions
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  1. 291
      libraries/SITL/SIM_Gimbal.cpp
  2. 108
      libraries/SITL/SIM_Gimbal.h

291
libraries/SITL/SIM_Gimbal.cpp
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/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
/*
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
gimbal simulator class for MAVLink gimbal
*/
#include "SIM_Aircraft.h"
#include "SIM_Gimbal.h"
#include <stdio.h>
extern const AP_HAL::HAL& hal;
Gimbal::Gimbal(const struct sitl_fdm &_fdm) :
fdm(_fdm),
target_address("127.0.0.1"),
target_port(5762),
lower_joint_limits(radians(-40), radians(-135), radians(-7.5)),
upper_joint_limits(radians(40), radians(45), radians(7.5)),
travelLimitGain(20),
seen_heartbeat(false),
seen_gimbal_control(false),
mav_socket(false)
{
memset(&mavlink, 0, sizeof(mavlink));
dcm.from_euler(radians(fdm.rollDeg), radians(fdm.pitchDeg), radians(fdm.yawDeg));
}
/*
update the gimbal state
*/
void Gimbal::update(void)
{
// calculate delta time in seconds
uint32_t now_us = hal.scheduler->micros();
float delta_t = (now_us - last_update_us) * 1.0e-6f;
last_update_us = now_us;
Matrix3f vehicle_dcm;
vehicle_dcm.from_euler(radians(fdm.rollDeg), radians(fdm.pitchDeg), radians(fdm.yawDeg));
Vector3f vehicle_gyro = Vector3f(radians(fdm.rollRate),
radians(fdm.pitchRate),
radians(fdm.yawRate));
Vector3f vehicle_accel_body = Vector3f(fdm.xAccel, fdm.yAccel, fdm.zAccel);
// take a copy of the demanded rates to bypass the limiter function for testing
Vector3f demRateRaw = demanded_angular_rate;
// 1) Rotate the copters rotation rates into the gimbals frame of reference
// copterAngRate_G = transpose(DCMgimbal)*DCMcopter*copterAngRate
Vector3f copterAngRate_G = dcm.transposed()*vehicle_dcm*vehicle_gyro;
// 2) Subtract the copters body rates to obtain a copter relative rotational
// rate vector (X,Y,Z) in gimbal sensor frame
// relativeGimbalRate(X,Y,Z) = gimbalRateDemand - copterAngRate_G
Vector3f relativeGimbalRate = demanded_angular_rate - copterAngRate_G;
// calculate joint angles (euler312 order)
// calculate copter -> gimbal rotation matrix
Matrix3f rotmat_copter_gimbal = dcm.transposed() * vehicle_dcm;
joint_angles = rotmat_copter_gimbal.transposed().to_euler312();
/* 4) For each of the three joints, calculate upper and lower rate limits
from the corresponding angle limits and current joint angles
upperRatelimit = (jointAngle - lowerAngleLimit) * travelLimitGain
lowerRatelimit = (jointAngle - upperAngleLimit) * travelLimitGain
travelLimitGain is equal to the inverse of the bump stop time constant and
should be set to something like 20 initially. If set too high it can cause
the rates to 'ring' when they the limiter is in force, particularly given
we are using a first order numerical integration.
*/
Vector3f upperRatelimit = -(joint_angles - upper_joint_limits) * travelLimitGain;
Vector3f lowerRatelimit = -(joint_angles - lower_joint_limits) * travelLimitGain;
/*
5) Calculate the gimbal joint rates (roll, elevation, azimuth)
gimbalJointRates(roll, elev, azimuth) = Matrix*relativeGimbalRate(X,Y,Z)
where matrix =
+- -+
| cos(elevAngle), 0, sin(elevAngle) |
| |
| sin(elevAngle) tan(rollAngle), 1, -cos(elevAngle) tan(rollAngle) |
| |
| sin(elevAngle) cos(elevAngle) |
| - --------------, 0, -------------- |
| cos(rollAngle) cos(rollAngle) |
+- -+
*/
float rollAngle = joint_angles.x;
float elevAngle = joint_angles.y;
Matrix3f matrix = Matrix3f(Vector3f(cosf(elevAngle), 0, sinf(elevAngle)),
Vector3f(sinf(elevAngle)*tanf(rollAngle), 1, -cosf(elevAngle)*tanf(rollAngle)),
Vector3f(-sinf(elevAngle)/cosf(rollAngle), 0, cosf(elevAngle)/cosf(rollAngle)));
Vector3f gimbalJointRates = matrix * relativeGimbalRate;
// 6) Apply the rate limits from 4)
gimbalJointRates.x = constrain_float(gimbalJointRates.x, lowerRatelimit.x, upperRatelimit.x);
gimbalJointRates.y = constrain_float(gimbalJointRates.y, lowerRatelimit.y, upperRatelimit.y);
gimbalJointRates.z = constrain_float(gimbalJointRates.z, lowerRatelimit.z, upperRatelimit.z);
/*
7) Convert the modified gimbal joint rates to body rates (still copter
relative)
relativeGimbalRate(X,Y,Z) = Matrix * gimbalJointRates(roll, elev, azimuth)
where Matrix =
+- -+
| cos(elevAngle), 0, -cos(rollAngle) sin(elevAngle) |
| |
| 0, 1, sin(rollAngle) |
| |
| sin(elevAngle), 0, cos(elevAngle) cos(rollAngle) |
+- -+
*/
matrix = Matrix3f(Vector3f(cosf(elevAngle), 0, -cosf(rollAngle)*sinf(elevAngle)),
Vector3f(0, 1, sinf(rollAngle)),
Vector3f(sinf(elevAngle), 0, cosf(elevAngle)*cosf(rollAngle)));
relativeGimbalRate = matrix * gimbalJointRates;
// 8) Add to the result from step 1) to obtain the demanded gimbal body rates
// in an inertial frame of reference
// demandedGimbalRatesInertial(X,Y,Z) = relativeGimbalRate(X,Y,Z) + copterAngRate_G
// Vector3f demandedGimbalRatesInertial = relativeGimbalRate + copterAngRate_G;
// for the moment we will set gyros equal to demanded_angular_rate
gimbal_angular_rate = demRateRaw; // demandedGimbalRatesInertial + true_gyro_bias - supplied_gyro_bias
// update rotation of the gimbal
dcm.rotate(gimbal_angular_rate*delta_t);
dcm.normalize();
// calculate copter -> gimbal rotation matrix
rotmat_copter_gimbal = dcm.transposed() * vehicle_dcm;
// calculate joint angles (euler312 order)
joint_angles = rotmat_copter_gimbal.transposed().to_euler312();
// update observed gyro
gyro = gimbal_angular_rate + true_gyro_bias;
// update delta_angle (integrate)
delta_angle += gyro * delta_t;
// calculate accel in gimbal body frame
Vector3f copter_accel_earth = vehicle_dcm * vehicle_accel_body;
Vector3f accel = dcm.transposed() * copter_accel_earth;
// integrate velocity
delta_velocity += accel * delta_t;
// see if we should do a report
send_report();
}
/*
send a report to the vehicle control code over MAVLink
*/
void Gimbal::send_report(void)
{
if (!mavlink.connected && mav_socket.connect(target_address, target_port)) {
::printf("Gimbal connected to %s:%u\n", target_address, (unsigned)target_port);
mavlink.connected = true;
}
if (!mavlink.connected) {
return;
}
// check for incoming MAVLink messages
uint8_t buf[100];
ssize_t ret;
while ((ret=mav_socket.recv(buf, sizeof(buf), 0)) > 0) {
for (uint8_t i=0; i<ret; i++) {
mavlink_message_t msg;
mavlink_status_t status;
if (mavlink_frame_char_buffer(&mavlink.rxmsg, &mavlink.status,
buf[i],
&msg, &status) == MAVLINK_FRAMING_OK) {
switch (msg.msgid) {
case MAVLINK_MSG_ID_HEARTBEAT: {
if (!seen_heartbeat) {
seen_heartbeat = true;
vehicle_component_id = msg.compid;
vehicle_system_id = msg.sysid;
::printf("Gimbal using srcSystem %u\n", (unsigned)vehicle_system_id);
}
break;
}
case MAVLINK_MSG_ID_GIMBAL_CONTROL: {
mavlink_gimbal_control_t pkt;
mavlink_msg_gimbal_control_decode(&msg, &pkt);
demanded_angular_rate = Vector3f(pkt.demanded_rate_x,
pkt.demanded_rate_y,
pkt.demanded_rate_z);
// no longer supply a bias
supplied_gyro_bias.zero();
seen_gimbal_control = true;
break;
}
}
}
}
}
if (!seen_heartbeat) {
return;
}
uint32_t now = hal.scheduler->millis();
mavlink_message_t msg;
uint16_t len;
if (now - last_heartbeat_ms >= 1000) {
mavlink_heartbeat_t heartbeat;
heartbeat.type = MAV_TYPE_GIMBAL;
heartbeat.autopilot = MAV_AUTOPILOT_ARDUPILOTMEGA;
heartbeat.base_mode = 0;
heartbeat.system_status = 0;
heartbeat.mavlink_version = 0;
heartbeat.custom_mode = 0;
/*
save and restore sequence number for chan0, as it is used by
generated encode functions
*/
mavlink_status_t *chan0_status = mavlink_get_channel_status(MAVLINK_COMM_0);
uint8_t saved_seq = chan0_status->current_tx_seq;
chan0_status->current_tx_seq = mavlink.seq;
len = mavlink_msg_heartbeat_encode(vehicle_system_id,
vehicle_component_id,
&msg, &heartbeat);
chan0_status->current_tx_seq = saved_seq;
mav_socket.send(&msg.magic, len);
last_heartbeat_ms = now;
}
/*
send a GIMBAL_REPORT message
*/
uint32_t now_us = hal.scheduler->micros();
if (now_us - last_report_us > reporting_period_ms*1000UL) {
mavlink_gimbal_report_t gimbal_report;
float delta_time = (now_us - last_report_us) * 1.0e-6f;
last_report_us = now_us;
gimbal_report.target_system = vehicle_system_id;
gimbal_report.target_component = vehicle_component_id;
gimbal_report.delta_time = delta_time;
gimbal_report.delta_angle_x = delta_angle.x;
gimbal_report.delta_angle_y = delta_angle.y;
gimbal_report.delta_angle_z = delta_angle.z;
gimbal_report.delta_velocity_x = delta_velocity.x;
gimbal_report.delta_velocity_y = delta_velocity.y;
gimbal_report.delta_velocity_z = delta_velocity.z;
gimbal_report.joint_roll = joint_angles.x;
gimbal_report.joint_el = joint_angles.y;
gimbal_report.joint_az = joint_angles.z;
mavlink_status_t *chan0_status = mavlink_get_channel_status(MAVLINK_COMM_0);
uint8_t saved_seq = chan0_status->current_tx_seq;
chan0_status->current_tx_seq = mavlink.seq;
len = mavlink_msg_gimbal_report_encode(vehicle_system_id,
vehicle_component_id,
&msg, &gimbal_report);
chan0_status->current_tx_seq = saved_seq;
mav_socket.send(&msg.magic, len);
delta_velocity.zero();
delta_angle.zero();
}
}

108
libraries/SITL/SIM_Gimbal.h
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/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
/*
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
gimbal simulator class
*/
#ifndef _SIM_GIMBAL_H
#define _SIM_GIMBAL_H
#include "SIM_Aircraft.h"
#include <utility/Socket.h>
class Gimbal
{
public:
Gimbal(const struct sitl_fdm &_fdm);
void update(void);
private:
const struct sitl_fdm &fdm;
const char *target_address;
const uint16_t target_port;
// rotation matrix (gimbal body -> earth)
Matrix3f dcm;
// time of last update
uint32_t last_update_us;
// true angular rate of gimbal in body frame (rad/s)
Vector3f gimbal_angular_rate;
// observed angular rate (including biases)
Vector3f gyro;
/* joint angles, in radians. in yaw/roll/pitch order. Relative to fwd.
So 0,0,0 points forward.
Pi/2,0,0 means pointing right
0, Pi/2, 0 means pointing fwd, but rolled 90 degrees to right
0, 0, -Pi/2, means pointing down
*/
Vector3f joint_angles;
// physical constraints on joint angles in (roll, pitch, azimuth) order
Vector3f lower_joint_limits;
Vector3f upper_joint_limits;
const float travelLimitGain;
// true gyro bias
Vector3f true_gyro_bias;
// reporting variables. gimbal pushes these to vehicle code over
// MAVLink at approx 100Hz
// reporting period in ms
static const float reporting_period_ms = 10;
// integral of gyro vector over last time interval. In radians
Vector3f delta_angle;
// integral of accel vector over last time interval. In m/s
Vector3f delta_velocity;
/*
control variables from the vehicle
*/
// angular rate in rad/s. In body frame of gimbal
Vector3f demanded_angular_rate;
// gyro bias provided by EKF on vehicle. In rad/s.
// Should be subtracted from the gyro readings to get true body
// rotatation rates
Vector3f supplied_gyro_bias;
uint32_t last_report_us;
uint32_t last_heartbeat_ms;
bool seen_heartbeat;
bool seen_gimbal_control;
uint8_t vehicle_system_id;
uint8_t vehicle_component_id;
SocketAPM mav_socket;
struct {
// socket to telem2 on aircraft
bool connected;
mavlink_message_t rxmsg;
mavlink_status_t status;
uint8_t seq;
} mavlink;
void send_report(void);
};
#endif // _SIM_GIMBAL_H
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