sickld.cpp

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/*
 * Authors: Nick Hillier and Fred Pauling (CSIRO, 2011)
 * 
 * Based on the sicklms.cpp from the sicktoolbox_wrapper ROS package
 * and the sample code from the sicktoolbox manual.
 * 
 * Released under BSD license.
 */ 

#include <iostream>
#include <sicktoolbox/SickLD.hh>
#include "ros/ros.h"
#include "sensor_msgs/LaserScan.h"
#include <deque>

#define DEG2RAD(x) ((x)*M_PI/180.)

using namespace std;
using namespace SickToolbox;

// TODO: refactor these functions into a common util lib (similar to code in sicklms.cpp)
void publish_scan(ros::Publisher *pub, double *range_values,
                  uint32_t n_range_values, unsigned int *intensity_values,
                  uint32_t n_intensity_values, ros::Time start,
                  double scan_time, bool inverted, float angle_min,
                  float angle_max, std::string frame_id)
{
  static int scan_count = 0;
  sensor_msgs::LaserScan scan_msg;
  scan_msg.header.frame_id = frame_id;
  scan_count++;
  if (inverted) { // assumes scan window at the bottom
    scan_msg.angle_min = angle_max;
    scan_msg.angle_max = angle_min;
  } else {
    scan_msg.angle_min = angle_min;
    scan_msg.angle_max = angle_max;
  }
  scan_msg.angle_increment = (scan_msg.angle_max - scan_msg.angle_min) / (double)(n_range_values-1);
  scan_msg.scan_time = scan_time;
  scan_msg.time_increment = scan_time / n_range_values;
  scan_msg.range_min = 0.5;
  scan_msg.range_max = 250.;
  scan_msg.ranges.resize(n_range_values);
  scan_msg.header.stamp = start;
  for (size_t i = 0; i < n_range_values; i++) {
    scan_msg.ranges[i] = (float)range_values[i];
  }
  scan_msg.intensities.resize(n_intensity_values);
  for (size_t i = 0; i < n_intensity_values; i++) {
    scan_msg.intensities[i] = (float)intensity_values[i];
  }
  pub->publish(scan_msg);
}

// A complimentary filter to get a (much) better time estimate, does not
// calibrate out constant network latency delays, but does get rid of 
// timming jitter to get better timing estimates than the 
// communicated clock resolution (which is only 1ms)
class smoothtime { 
    protected:
        ros::Time smoothtime_prev, smoothed_timestamp;
        double time_smoothing_factor;
        double error_threshold;
    public:
        smoothtime(){
            time_smoothing_factor = 0.95; 
            error_threshold = .50; 
        }
        void set_smoothing_factor(double smoothing_factor){ 
            time_smoothing_factor = smoothing_factor;
        }
        void set_error_threshold(double err_threshold){ 
            error_threshold = err_threshold;
        }
        ros::Time smooth_timestamp(ros::Time recv_timestamp, ros::Duration expctd_dur) {
            if (smoothtime_prev.is_zero() == true) {
                smoothed_timestamp = recv_timestamp;
            } else {
                smoothed_timestamp = smoothtime_prev + expctd_dur;
                double err = (recv_timestamp - smoothed_timestamp).toSec();
                double time_error_threshold = expctd_dur.toSec() * error_threshold;
                if ((time_smoothing_factor > 0) && (fabs(err) < time_error_threshold)){
                    ros::Duration correction = ros::Duration(err * (1 - time_smoothing_factor));
                    smoothed_timestamp += correction;
                } else {
                    // error too high, or smoothing disabled - set smoothtime to last timestamp
                    smoothed_timestamp = recv_timestamp;
                }
            }
            smoothtime_prev = smoothed_timestamp;
            return smoothed_timestamp;
        }
};

class averager {
    protected:
        std::deque<double> deq;
        unsigned int max_len;
        double sum;
    public:
        averager(int max_len = 50){
            this->max_len = max_len;
        }
        void add_new(double data) {
            deq.push_back(data);
            sum += data;
            if (deq.size() > max_len) {
                sum -= deq.front();
                deq.pop_front();
            }
        }
        double get_mean() {
            return sum/deq.size();
        }
};
        

int main(int argc, char *argv[]) {
    ros::init(argc, argv, "sickld");
    int port;
    std::string ipaddress;
    std::string frame_id;
    bool inverted;
    int sick_motor_speed = 5;//10; // Hz
    double sick_step_angle = 1.5;//0.5;//0.25; // deg (0.125 = no gaps between spots)
    double active_sector_start_angle = 0;
    double active_sector_stop_angle = 300;//269.75;
    double smoothing_factor, error_threshold;
    ros::NodeHandle nh;
        ros::NodeHandle nh_ns("~");
        ros::Publisher scan_pub = nh.advertise<sensor_msgs::LaserScan>("scan", 1);
        nh_ns.param("port", port, DEFAULT_SICK_TCP_PORT);
        nh_ns.param("ipaddress", ipaddress, (std::string)DEFAULT_SICK_IP_ADDRESS);
        nh_ns.param("inverted", inverted, false);
        nh_ns.param<std::string>("frame_id", frame_id, "laser");
    nh_ns.param("timer_smoothing_factor", smoothing_factor, 0.97);
    nh_ns.param("timer_error_threshold", error_threshold, 0.5);
    nh_ns.param("resolution", sick_step_angle, 1.0); 
    nh_ns.param("start_angle", active_sector_start_angle, 0.); 
    nh_ns.param("stop_angle", active_sector_stop_angle, 300.); 
    nh_ns.param("scan_rate", sick_motor_speed, 10); 
    /* Define buffers for return values */
    double range_values[SickLD::SICK_MAX_NUM_MEASUREMENTS] = {0};
    unsigned int intensity_values[SickLD::SICK_MAX_NUM_MEASUREMENTS] = {0};
    /* Define buffers to hold sector specific data */
    unsigned int num_measurements = {0};
    unsigned int sector_start_timestamp = {0};
        unsigned int sector_stop_timestamp = {0};
    double sector_step_angle = {0};
    double sector_start_angle = {0};
    double sector_stop_angle = {0};
    /* Instantiate the object */
    SickLD sick_ld(ipaddress.c_str(),port);
    try {
        /* Initialize the device */
        sick_ld.Initialize();
        // TODO: do some calls to setup the device - e.g. scan rate.
        try {
            sick_ld.SetSickGlobalParamsAndScanAreas((unsigned int)sick_motor_speed,
                                          sick_step_angle,
                                          &active_sector_start_angle,
                                          &active_sector_stop_angle,
                                          (unsigned int)1);
        } catch (...) {
            ROS_ERROR("Configuration error");
            return -1;
        }
        smoothtime smoothtimer;
        averager avg_fulldur, avg_scandur;
        smoothtimer.set_smoothing_factor(smoothing_factor);
        smoothtimer.set_error_threshold(error_threshold);
        ros::Time last_start_scan_time;
        unsigned int last_sector_stop_timestamp = 0;
        double full_duration;
        while (ros::ok()) {
            /* Grab the measurements (from all sectors) */
            sick_ld.GetSickMeasurements(range_values,
                                        intensity_values,
                                        &num_measurements,
                                        NULL,
                                        NULL,
                                        &sector_step_angle,
                                        &sector_start_angle,
                                        &sector_stop_angle,
                                        &sector_start_timestamp,
                                        &sector_stop_timestamp
                                        );
            ros::Time end_scan_time = ros::Time::now();
            
            double scan_duration = (sector_stop_timestamp - sector_start_timestamp) * 1e-3;
            avg_scandur.add_new(scan_duration);
            scan_duration = avg_scandur.get_mean();
            
            if (last_sector_stop_timestamp == 0) {
                full_duration = 1./((double)sick_motor_speed);
            } else {
                full_duration = (sector_stop_timestamp - last_sector_stop_timestamp) * 1e-3;
            }
            avg_fulldur.add_new(full_duration);
            full_duration = avg_fulldur.get_mean();
            
            ros::Time smoothed_end_scan_time = smoothtimer.smooth_timestamp(end_scan_time, ros::Duration(full_duration));
            ros::Time start_scan_time = smoothed_end_scan_time - ros::Duration(scan_duration);
            
            publish_scan(&scan_pub, range_values, num_measurements, intensity_values,
                   num_measurements, start_scan_time, scan_duration, inverted,
                   DEG2RAD((float)sector_start_angle), DEG2RAD((float)sector_stop_angle), frame_id);

            ROS_DEBUG_STREAM("Num meas: " << num_measurements
                 << " smoothed start T: " << start_scan_time
                 << " smoothed rate: " << 1./(start_scan_time - last_start_scan_time).toSec()
                 << " raw start T: " << sector_start_timestamp
                 << " raw stop T: " << sector_stop_timestamp
                 << " dur: " << full_duration
                 << " step A: " << sector_step_angle
                 << " start A: " << sector_start_angle
                 << " stop A: " << sector_stop_angle);
            last_start_scan_time = start_scan_time;
            last_sector_stop_timestamp = sector_stop_timestamp;
                        ros::spinOnce();
        }
        /* Uninitialize the device */
        sick_ld.Uninitialize();
    }
    catch(...) {
        ROS_ERROR("Error");
        return -1;
    }
    return 0;
}