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mirror of https://gitlab.com/obbart/universal_robots_ros_driver.git synced 2026-04-12 11:00:47 +02:00

Adds Safe Trajectory Follower implementation

Safe Trajectory Follower implements different approach for controlling
the robot. Rather than calculate the interpolation steps in the driver
and send the small interpolated steps over the network to the URScript
program with 500Hz frequency, the coarser MoveIt trajectory is sent
(with few Hz) and the interpolation steps are calculated by the
URScript.

The algorithm for time progress has also built-in protection against
any delays induced by load on the driver, network or URControl - it
will never "catch-up" dangerously when such delay are introduced,
It will rather pause and wait for the next small interpolation step
instructions and re-start the move slower - never skipping any
interpolated steps.

Those changes make Safe Trajectory Follower much more resilient to
network communication problems and removes any superficial requirements
for the network setup, kernel latency and no-load-requirement for the
driver's PC - making it much more suitable for research, development
and quick iteration loops. It works reliably even over WiFi.
This commit is contained in:
Jarek Potiuk
2017-12-29 09:37:56 +01:00
parent f71c83c649
commit 5dcef72415
14 changed files with 734 additions and 31 deletions

View File

@@ -1,7 +1,7 @@
#include "ur_modern_driver/ros/action_server.h"
#include <cmath>
ActionServer::ActionServer(TrajectoryFollower& follower, std::vector<std::string>& joint_names, double max_velocity)
ActionServer::ActionServer(TrajectoryFollowerInterface& follower, std::vector<std::string>& joint_names, double max_velocity)
: as_(nh_, "follow_joint_trajectory", boost::bind(&ActionServer::onGoal, this, _1),
boost::bind(&ActionServer::onCancel, this, _1), false)
, joint_names_(joint_names)
@@ -307,6 +307,7 @@ void ActionServer::trajectoryThread()
Result res;
LOG_INFO("Attempting to start follower %p", &follower_);
if (follower_.start())
{
if (follower_.execute(trajectory, interrupt_traj_))

View File

@@ -0,0 +1,515 @@
#include "ur_modern_driver/ros/safe_trajectory_follower.h"
#include <endian.h>
#include <cmath>
#include <ros/ros.h>
static const std::array<double, 6> EMPTY_VALUES = {0.0, 0.0, 0.0, 0.0, 0.0, 0.0};
static const std::string TIME_INTERVAL("{{TIME_INTERVAL}}");
static const std::string SERVOJ_TIME("{{SERVOJ_TIME}}");
static const std::string SERVOJ_TIME_WAITING("{{SERVOJ_TIME_WAITING}}");
static const std::string MAX_WAITING_TIME("{{MAX_WAITING_TIME}}");
static const std::string DEBUG("{{DEBUG}}");
static const std::string MORE_DEBUG("{{MORE_DEBUG}}");
static const std::string SERVOJ_GAIN("{{SERVOJ_GAIN}}");
static const std::string SERVOJ_LOOKAHEAD_TIME("{{SERVOJ_LOOKAHEAD_TIME}}");
static const std::string REVERSE_IP("{{REVERSE_IP}}");
static const std::string REVERSE_PORT("{{REVERSE_PORT}}");
static const std::string POSITION_PROGRAM = R"(
def driveRobotSafeTrajectory():
global JOINT_NUM = 6
global TIME_INTERVAL = {{TIME_INTERVAL}}
global SERVOJ_TIME = {{SERVOJ_TIME}}
global SERVOJ_TIME_WAITING = {{SERVOJ_TIME_WAITING}}
global MAX_WAITING_TIME = {{MAX_WAITING_TIME}}
global DEBUG = {{DEBUG}}
global MORE_DEBUG = {{MORE_DEBUG}}
global EMPTY_VALUES = [0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
global SERVOJ_GAIN = {{SERVOJ_GAIN}}
global SERVOJ_LOOKAHEAD_TIME = {{SERVOJ_LOOKAHEAD_TIME}}
global CONNECTION_NAME = "reverse_connection"
global REVERSE_IP = "{{REVERSE_IP}}"
global REVERSE_PORT = {{REVERSE_PORT}}
# NOTE All the global variables here are accessed by different threads
# therefore they should be accessed within critical section. Those variables
# are all prefixed with g_ . Whenever their values are needed they are copied
# to similarly named l_ variable. Copying happens inside the critical section
# and l_values might be used outside of it. This needs to be confirmed with UR
# about the semantics of assignment operator (copying or by reference?).
# Hopefully it's copying :).
#
# Please make sure to keep that pattern and do not access the global variables
# outside of the critical section
#
# TO DO: Are those assignments by references or copies? We will find out soon
# If not then assigning positions would not work either
global g_position_previous = EMPTY_VALUES
global g_position_target = EMPTY_VALUES
global g_position_next = EMPTY_VALUES
global g_velocity_previous = EMPTY_VALUES
global g_velocity_target = EMPTY_VALUES
global g_velocity_next = EMPTY_VALUES
global g_time_previous = 0.0
global g_time_target = 0.0
global g_time_next = 0.0
global g_num_previous = -1
global g_num_target = -1
global g_num_next = -1
global g_received_waypoints_number = -1
global g_requested_waypoints_number = -1
global g_total_elapsed_time = 0
global g_stopping = False
def send_message(message):
socket_send_string(message, CONNECTION_NAME)
socket_send_byte(10, CONNECTION_NAME)
end
def is_waypoint_sentinel(waypoint):
local l_previous_index = 2
while l_previous_index < 1 + JOINT_NUM * 2 + 2: # Note - we do not check first two which are non-zero
if waypoint[l_previous_index] != 0.0:
return False
end
l_previous_index = l_previous_index + 1
end
return True
end
def interpolate(time_within_segment, total_segment_time, start_pos, l_end_pos, l_start_vel, end_vel):
local a = start_pos
local b = l_start_vel
local c = (-3 * a + 3 * l_end_pos - 2 * total_segment_time * b - total_segment_time * end_vel) / pow(total_segment_time, 2)
local d = (2 * a - 2 * l_end_pos + total_segment_time * b + total_segment_time * end_vel) / pow(total_segment_time, 3)
return a + b * time_within_segment + c * pow(time_within_segment, 2) + d * pow(time_within_segment, 3)
end
def add_next_waypoint(waypoint):
enter_critical
# Rotate the values received so far:
# target -> previous
g_position_previous = g_position_target
g_velocity_previous = g_velocity_target
g_time_previous = g_time_target
g_num_previous = g_num_target
# next -> previous
g_position_target = g_position_next
g_velocity_target = g_velocity_next
g_time_target = g_time_next
g_num_target = g_num_next
# Decode the array received into next
# waypoint 0 is number of entries in the received array
g_num_next = waypoint[1]
g_position_next = [waypoint[2], waypoint[3], waypoint[4], waypoint[5], waypoint[6], waypoint[7]]
g_velocity_next = [waypoint[8], waypoint[9], waypoint[10], waypoint[11], waypoint[12], waypoint[13]]
g_time_next = waypoint[14]
# store latest received waypoint number so that controlling thread knows it's been received already
g_received_waypoints_number = g_num_next
if DEBUG:
local l_received_waypoints_number = g_received_waypoints_number
local l_waypoint = waypoint
end
exit_critical
if DEBUG:
textmsg("Received waypoint:")
textmsg(l_received_waypoints_number)
textmsg(l_waypoint)
end
end
# Thread controlling the motor. In the loop it checks first if it received the
# requested waypoints and until it does, it syncs doing noting to the motor
# once it received all up to requested waypoints it executes interpolation
# between PREVIOUS AND TARGET points received and rquests the next waypoint request
# to be sent.
thread controllingThread():
local l_received_waypoints_number = -1
local l_requested_waypoints_number = -1
local l_stopped = False
local l_current_position = get_actual_joint_positions()
enter_critical
g_requested_waypoints_number = 2
exit_critical
while True:
enter_critical
l_requested_waypoints_number = g_requested_waypoints_number
l_received_waypoints_number = g_received_waypoints_number
exit_critical
local l_max_waiting_time_left = MAX_WAITING_TIME
# if expected waypoint number not yet received wait so that receiving thread has time to receive it
while l_received_waypoints_number < l_requested_waypoints_number and l_max_waiting_time_left > 0:
if DEBUG:
textmsg("Waiting for the received waypoints number to catch up (received/requested):")
textmsg(l_received_waypoints_number)
textmsg(l_requested_waypoints_number)
end
# Keep robot in l_current position for short time and check if the next waipoint arrived
servoj(l_current_position,t=SERVOJ_TIME_WAITING,lookahead_time=SERVOJ_LOOKAHEAD_TIME,gain=SERVOJ_GAIN)
enter_critical
l_received_waypoints_number = g_received_waypoints_number
exit_critical
l_max_waiting_time_left = l_max_waiting_time_left - SERVOJ_TIME_WAITING
end
if l_max_waiting_time_left <= 0:
textmsg("Closing the connection on waiting too long.")
socket_close(CONNECTION_NAME)
halt
end
# OK. We received next point, copy the required global variables into local ones
enter_critical
local l_start_pos = g_position_previous
local l_start_vel = g_velocity_previous
local l_start_time = g_time_previous
local l_start_num= g_num_previous
local l_end_pos = g_position_target
local l_end_vel = g_velocity_target
local l_end_time = g_time_target
local l_end_num = g_num_target
local l_total_elapsed_time = g_total_elapsed_time
# Note we deliberately only read "stopping" state here and not update it below
# so that stopping flag takes effect only after one additional interpolation loop is complete
# and all points of the trajectory are processeed
local l_stopping_after_next_interpolation = g_stopping
# And increasing the global requested number - informs sender thread that it needs to ask for it
g_requested_waypoints_number = g_requested_waypoints_number + 1
exit_critical
if DEBUG:
textmsg("Starting interpolation. Segment from/to:")
textmsg(l_start_num)
textmsg(l_end_num)
textmsg("Current time:")
textmsg(l_total_elapsed_time)
textmsg("Starting/Ending segment time:")
textmsg(l_start_time)
textmsg(l_end_time)
end
l_current_position = l_start_pos
local l_total_segment_time = l_end_time - l_start_time
# Here perform the interpolation loop
while l_total_elapsed_time <= l_end_time:
if MORE_DEBUG:
textmsg("Next step of interpolation:")
end
local l_segment_elapsed_time = l_total_elapsed_time - l_start_time
# Calculate interpolation for all joints
j = 0
while j < JOINT_NUM:
l_current_position[j] = interpolate(l_segment_elapsed_time, l_total_segment_time, l_start_pos[j], l_end_pos[j], l_start_vel[j], l_end_vel[j])
j = j + 1
end
if MORE_DEBUG:
textmsg("Next step of interpolated position:")
textmsg(l_current_position)
textmsg("Current time:")
textmsg(l_total_elapsed_time)
textmsg("Running servoj command:")
end
servoj(l_current_position,t=SERVOJ_TIME,lookahead_time=SERVOJ_LOOKAHEAD_TIME,gain=SERVOJ_GAIN)
enter_critical
g_total_elapsed_time = g_total_elapsed_time + TIME_INTERVAL
l_total_elapsed_time = g_total_elapsed_time
exit_critical
if MORE_DEBUG:
textmsg("Finishing interpolation step at time:")
textmsg(l_total_elapsed_time)
end
end
if DEBUG:
textmsg("Ending interpolation segment at time:")
textmsg(l_total_elapsed_time)
end
if l_stopping_after_next_interpolation:
textmsg("Stopping the controlling thread on signal from receiving thread after one interpolation loop.")
break
end
end
textmsg("Ending controlling thread")
end
# This thread sends requested waypoints number to the client when requested number is changed
# It will send all the numbers from [already sent + 1, g_requested_waypoints_number] and waits
# until requested waypoints number increases
thread sendingThread():
local controlling_thread = run controllingThread()
local l_sent_waypoints_number = -1
local l_requested_waypoints_number = -1
local l_stopping = False
enter_critical
l_requested_waypoints_number = g_requested_waypoints_number
l_stopping = g_stopping
exit_critical
while not l_stopping:
# wait until we have more requested waypoints to send than actually sent ones
while l_sent_waypoints_number == l_requested_waypoints_number and not l_stopping:
sleep(SERVOJ_TIME_WAITING)
enter_critical
l_requested_waypoints_number = g_requested_waypoints_number
l_stopping = g_stopping
exit_critical
end
if l_stopping:
break
end
send_message(l_sent_waypoints_number + 1)
l_sent_waypoints_number = l_sent_waypoints_number + 1
if DEBUG:
textmsg("Sent waypoint request number:")
textmsg(l_sent_waypoints_number)
end
end
textmsg("Joining controlling thread")
join controlling_thread
textmsg("Ending Sending thread")
end
# Receiving thread - it will receive the next trajectory point over the TCP connection
# It will increase the received waipoints_number on each request.
thread receivingThread():
local sending_thread = run sendingThread()
while True:
waypoint_received = socket_read_ascii_float(14, CONNECTION_NAME)
if waypoint_received[0] == 0:
# No new waypoint requested for the last 2 seconds
textmsg("Not received trajectory for the last 2 seconds. Quitting")
enter_critical
g_stopping = True
exit_critical
break
elif waypoint_received[0] != JOINT_NUM * 2 + 2:
textmsg("Received wrong number of floats in trajectory. This is certainly not OK.")
textmsg(waypoint_received[0])
enter_critical
g_stopping = True
exit_critical
break
elif is_waypoint_sentinel(waypoint_received):
add_next_waypoint(waypoint_received)
textmsg("Received sentinel waypoint. Finishing.")
enter_critical
g_stopping = True
g_received_waypoints_number = g_received_waypoints_number + 1
exit_critical
break
end
add_next_waypoint(waypoint_received)
end
textmsg("Joining sendingThread")
join sending_thread
textmsg("Ending Receiving thread")
end
textmsg("Opening socket")
socket_open(REVERSE_IP, REVERSE_PORT, CONNECTION_NAME)
textmsg("Socket opened")
receiving_thread = run receivingThread()
textmsg("Joining receiving_thread")
join receiving_thread
textmsg("Closing reverse connection")
socket_close(CONNECTION_NAME)
textmsg("Exiting the program")
end
)";
SafeTrajectoryFollower::SafeTrajectoryFollower(URCommander &commander, std::string &reverse_ip, int reverse_port,
bool version_3)
: running_(false)
, commander_(commander)
, server_(reverse_port)
, time_interval_(0.008)
, servoj_time_(0.008)
, servoj_time_waiting_(0.001)
, max_waiting_time_(2.0)
, servoj_gain_(300.0)
, servoj_lookahead_time_(0.03)
, debug_(false)
, more_debug_(false)
{
ros::param::get("~time_interval", time_interval_);
ros::param::get("~servoj_time", servoj_time_);
ros::param::get("~servoj_time_waiting", servoj_time_waiting_);
ros::param::get("~max_waiting_time", max_waiting_time_);
ros::param::get("~servoj_gain", servoj_gain_);
ros::param::get("~servoj_lookahead_time", servoj_lookahead_time_);
ros::param::get("~debug", debug_);
ros::param::get("~more_debug", more_debug_);
std::string res(POSITION_PROGRAM);
std::ostringstream out;
if (!version_3) {
LOG_ERROR("Safe Trajectory Follower only works for interface version > 3");
std::exit(-1);
}
res.replace(res.find(TIME_INTERVAL), TIME_INTERVAL.length(), std::to_string(time_interval_));
res.replace(res.find(SERVOJ_TIME_WAITING), SERVOJ_TIME_WAITING.length(), std::to_string(servoj_time_waiting_));
res.replace(res.find(SERVOJ_TIME), SERVOJ_TIME.length(), std::to_string(servoj_time_));
res.replace(res.find(MAX_WAITING_TIME), MAX_WAITING_TIME.length(), std::to_string(max_waiting_time_));
res.replace(res.find(SERVOJ_GAIN), SERVOJ_GAIN.length(), std::to_string(servoj_gain_));
res.replace(res.find(SERVOJ_LOOKAHEAD_TIME), SERVOJ_LOOKAHEAD_TIME.length(), std::to_string(servoj_lookahead_time_));
res.replace(res.find(DEBUG), DEBUG.length(), debug_ ? "True" : "False");
res.replace(res.find(MORE_DEBUG), MORE_DEBUG.length(), more_debug_ ? "True" : "False");
res.replace(res.find(REVERSE_IP), REVERSE_IP.length(), reverse_ip);
res.replace(res.find(REVERSE_PORT), REVERSE_PORT.length(), std::to_string(reverse_port));
program_ = res;
if (!server_.bind())
{
LOG_ERROR("Failed to bind server, the port %d is likely already in use", reverse_port);
std::exit(-1);
}
LOG_INFO("Safe Trajectory Follower is initialized!");
}
bool SafeTrajectoryFollower::start()
{
LOG_INFO("Starting SafeTrajectoryFollower");
if (running_)
return true; // not sure
LOG_INFO("Uploading trajectory program to robot");
if (!commander_.uploadProg(program_))
{
LOG_ERROR("Program upload failed!");
return false;
}
LOG_DEBUG("Awaiting incoming robot connection");
if (!server_.accept())
{
LOG_ERROR("Failed to accept incoming robot connection");
return false;
}
LOG_DEBUG("Robot successfully connected");
return (running_ = true);
}
bool SafeTrajectoryFollower::execute(const std::array<double, 6> &positions,
const std::array<double, 6> &velocities,
double sample_number, double time_in_seconds)
{
if (!running_)
return false;
std::ostringstream out;
out << "(";
out << sample_number << ",";
for (auto const &pos: positions)
{
out << pos << ",";
}
for (auto const &vel: velocities)
{
out << vel << ",";
}
out << time_in_seconds << ")\r\n";
// I know it's ugly but it's the most efficient and fastest way
// We have only ASCII characters and we can cast char -> uint_8
const std::string tmp = out.str();
const char *formatted_message = tmp.c_str();
const uint8_t *buf = (uint8_t *) formatted_message;
size_t written;
LOG_DEBUG("Sending message %s", formatted_message);
return server_.write(buf, strlen(formatted_message) + 1, written);
}
bool SafeTrajectoryFollower::execute(std::vector<TrajectoryPoint> &trajectory, std::atomic<bool> &interrupt)
{
if (!running_)
return false;
bool finished = false;
char* line[MAX_SERVER_BUF_LEN];
bool res = true;
while (!finished && !interrupt)
{
if (!server_.readLine((char *)line, MAX_SERVER_BUF_LEN))
{
LOG_DEBUG("Connection closed. Finishing!");
finished = true;
break;
}
unsigned int message_num=atoi((const char *) line);
LOG_DEBUG("Received request %i", message_num);
if (message_num < trajectory.size())
{
res = execute(trajectory[message_num].positions, trajectory[message_num].velocities,
message_num, trajectory[message_num].time_from_start.count() / 1e6);
} else
{
res = execute(EMPTY_VALUES, EMPTY_VALUES, message_num, 0.0);
}
if (!res)
{
finished = true;
}
}
return res;
}
void SafeTrajectoryFollower::stop()
{
if (!running_)
return;
server_.disconnectClient();
running_ = false;
}

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@@ -13,6 +13,7 @@
#include "ur_modern_driver/ros/rt_publisher.h"
#include "ur_modern_driver/ros/service_stopper.h"
#include "ur_modern_driver/ros/trajectory_follower.h"
#include "ur_modern_driver/ros/safe_trajectory_follower.h"
#include "ur_modern_driver/ros/urscript_handler.h"
#include "ur_modern_driver/ur/commander.h"
#include "ur_modern_driver/ur/factory.h"
@@ -25,6 +26,7 @@
static const std::string IP_ADDR_ARG("~robot_ip_address");
static const std::string REVERSE_PORT_ARG("~reverse_port");
static const std::string ROS_CONTROL_ARG("~use_ros_control");
static const std::string SAFE_TRAJECTORY_FOLLOWER("~use_safe_trajectory_follower");
static const std::string MAX_VEL_CHANGE_ARG("~max_vel_change");
static const std::string PREFIX_ARG("~prefix");
static const std::string BASE_FRAME_ARG("~base_frame");
@@ -53,6 +55,7 @@ public:
double max_vel_change;
int32_t reverse_port;
bool use_ros_control;
bool use_safe_trajectory_follower;
bool shutdown_on_disconnect;
};
@@ -92,6 +95,7 @@ bool parse_args(ProgArgs &args)
ros::param::param(MAX_VEL_CHANGE_ARG, args.max_vel_change, 15.0); // rad/s
ros::param::param(MAX_VEL_CHANGE_ARG, args.max_velocity, 10.0);
ros::param::param(ROS_CONTROL_ARG, args.use_ros_control, false);
ros::param::param(SAFE_TRAJECTORY_FOLLOWER, args.use_safe_trajectory_follower, false);
ros::param::param(PREFIX_ARG, args.prefix, std::string());
ros::param::param(BASE_FRAME_ARG, args.base_frame, args.prefix + "base_link");
ros::param::param(TOOL_FRAME_ARG, args.tool_frame, args.prefix + "tool0_controller");
@@ -134,7 +138,20 @@ int main(int argc, char **argv)
auto rt_commander = factory.getCommander(rt_stream);
vector<IConsumer<RTPacket> *> rt_vec{ &rt_pub };
TrajectoryFollower traj_follower(*rt_commander, local_ip, args.reverse_port, factory.isVersion3());
TrajectoryFollowerInterface *traj_follower(nullptr);
if (args.use_safe_trajectory_follower && !args.use_ros_control)
{
LOG_INFO("Use safe trajectory follower");
traj_follower = new SafeTrajectoryFollower(*rt_commander, local_ip, args.reverse_port,factory.isVersion3());
// We are leaking the follower here, but it's OK as this is once-a-lifetime event
}
else
{
LOG_INFO("Use standard trajectory follower");
traj_follower = new TrajectoryFollower(*rt_commander, local_ip, args.reverse_port, factory.isVersion3());
// We are leaking the follower here, but it's OK as this is once-a-lifetime event
}
INotifier *notifier(nullptr);
ROSController *controller(nullptr);
@@ -142,14 +159,15 @@ int main(int argc, char **argv)
if (args.use_ros_control)
{
LOG_INFO("ROS control enabled");
controller = new ROSController(*rt_commander, traj_follower, args.joint_names, args.max_vel_change, args.tcp_link);
// Note - we are sure that TrajectoryFollower is used here (see the args.use_ros_control above)
controller = new ROSController(*rt_commander, *((TrajectoryFollower *) traj_follower), args.joint_names, args.max_vel_change, args.tcp_link);
rt_vec.push_back(controller);
services.push_back(controller);
}
else
{
LOG_INFO("ActionServer enabled");
action_server = new ActionServer(traj_follower, args.joint_names, args.max_velocity);
action_server = new ActionServer(*traj_follower, args.joint_names, args.max_velocity);
rt_vec.push_back(action_server);
services.push_back(action_server);
}

View File

@@ -111,6 +111,16 @@ std::string TCPSocket::getIP()
return std::string(buf);
}
bool TCPSocket::read(char *character)
{
size_t read_chars;
// It's inefficient, but in our case we read very small messages
// and the overhead connected with reading character by character is
// negligible - adding buffering would complicate the code needlessly.
return read((uint8_t *) character, 1, read_chars);
}
bool TCPSocket::read(uint8_t *buf, size_t buf_len, size_t &read)
{
read = 0;

View File

@@ -86,3 +86,44 @@ bool URServer::write(const uint8_t* buf, size_t buf_len, size_t& written)
{
return client_.write(buf, buf_len, written);
}
bool URServer::readLine(char* buffer, size_t buf_len)
{
char *current_pointer = buffer;
char ch;
size_t total_read;
if (buf_len <= 0 || buffer == NULL) {
return false;
}
total_read = 0;
for (;;) {
if (client_.read(&ch))
{
if (total_read < buf_len - 1) // just in case ...
{
total_read ++;
*current_pointer++ = ch;
}
if (ch == '\n')
{
break;
}
}
else
{
if (total_read == 0)
{
return false;
}
else
{
break;
}
}
}
*current_pointer = '\0';
return true;
}