Line data    Source code

       1             : /*
       2             :    This program is free software: you can redistribute it and/or modify
       3             :    it under the terms of the GNU General Public License as published by
       4             :    the Free Software Foundation, either version 3 of the License, or
       5             :    (at your option) any later version.
       6             : 
       7             :    This program is distributed in the hope that it will be useful,
       8             :    but WITHOUT ANY WARRANTY; without even the implied warranty of
       9             :    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      10             :    GNU General Public License for more details.
      11             : 
      12             :    You should have received a copy of the GNU General Public License
      13             :    along with this program.  If not, see <http://www.gnu.org/licenses/>.
      14             :  */
      15             : /*
      16             :   simple Gripper (OpenGrab EPM) simulation class
      17             : */
      18             : 
      19             : #include "SIM_Gripper_EPM.h"
      20             : #include "AP_HAL/AP_HAL.h"
      21             : #include <stdio.h>
      22             : #include <AP_Math/AP_Math.h>
      23             : 
      24             : extern const AP_HAL::HAL& hal;
      25             : 
      26             : using namespace SITL;
      27             : 
      28             : // table of user settable parameters
      29             : const AP_Param::GroupInfo Gripper_EPM::var_info[] = {
      30             : 
      31             :     // @Param: ENABLE
      32             :     // @DisplayName: Gripper servo Sim enable/disable
      33             :     // @Description: Allows you to enable (1) or disable (0) the gripper servo simulation
      34             :     // @Values: 0:Disabled,1:Enabled
      35             :     // @User: Advanced
      36             :     AP_GROUPINFO("ENABLE", 0, Gripper_EPM, gripper_emp_enable, 0),
      37             : 
      38             :     // @Param: PIN
      39             :     // @DisplayName: Gripper emp pin
      40             :     // @Description: The pin number that the gripper emp is connected to. (start at 1)
      41             :     // @Range: 0 15
      42             :     // @User: Advanced
      43             :     AP_GROUPINFO("PIN", 1, Gripper_EPM, gripper_emp_servo_pin, -1),
      44             : 
      45             :     AP_GROUPEND
      46             : };
      47             : 
      48             : /*
      49             :   update gripper state
      50             :  */
      51           0 : void Gripper_EPM::update_servobased(int16_t gripper_pwm)
      52             : {
      53           0 :     if (!servo_based) {
      54           0 :         return;
      55             :     }
      56           0 :     if (gripper_pwm >= 0) {
      57           0 :         demand = (gripper_pwm - 1000) * 0.001f; // 0.0 - 1.0
      58           0 :         if (is_negative(demand)) { // never updated
      59           0 :             demand = 0.0f;
      60             :         }
      61             :     }
      62             : }
      63             : 
      64             : 
      65           0 : void Gripper_EPM::update_from_demand()
      66             : {
      67           0 :     const uint64_t now = AP_HAL::micros64();
      68           0 :     const float dt = (now - last_update_us) * 1.0e-6f;
      69             : 
      70             :     // decay the field
      71           0 :     field_strength = field_strength * (100.0f - field_decay_rate * dt) * 0.01f;
      72             : 
      73             :     // note that "demand" here is just an on/off switch; we only care
      74             :     // about which range it falls into
      75           0 :     if (demand > 0.6f) {
      76             :         // we are instructed to grip harder
      77           0 :         field_strength = field_strength + (100.0f - field_strength) * field_strength_slew_rate * 0.01f * dt;
      78           0 :     } else if (demand < 0.4f) {
      79             :         // we are instructed to loosen grip
      80           0 :         field_strength = field_strength * (100.0f - field_degauss_rate * dt) * 0.01f;
      81             :     } else {
      82             :         // neutral; no demanded change
      83             :     }
      84             : 
      85           0 :     if (should_report()) {
      86           0 :         hal.console->printf("demand=%f\n", demand);
      87           0 :         hal.console->printf("Field strength: %f%%\n", field_strength);
      88           0 :         hal.console->printf("Field strength: %f Tesla\n", tesla());
      89           0 :         last_report_us = now;
      90           0 :         reported_field_strength = field_strength;
      91             :     }
      92             : 
      93           0 :     last_update_us = now;
      94           0 : }
      95             : 
      96           0 : void Gripper_EPM::update(const struct sitl_input &input)
      97             : {
      98           0 :     const int16_t gripper_pwm = gripper_emp_servo_pin >= 1 ? input.servos[gripper_emp_servo_pin-1] : -1;
      99             : 
     100           0 :     update_servobased(gripper_pwm);
     101             : 
     102           0 :     update_from_demand();
     103           0 : }
     104             : 
     105             : 
     106           0 : bool Gripper_EPM::should_report() const
     107             : {
     108           0 :     if (AP_HAL::micros64() - last_report_us < report_interval) {
     109           0 :         return false;
     110             :     }
     111             : 
     112           0 :     if (fabsf(reported_field_strength - field_strength) > 10.0) {
     113           0 :         return true;
     114             :     }
     115             : 
     116           0 :     return false;
     117             : }
     118             : 
     119           0 : float Gripper_EPM::tesla() const
     120             : {
     121             :     // https://en.wikipedia.org/wiki/Orders_of_magnitude_(magnetic_field)
     122             :     // 200N lifting capacity ~= 2.5T
     123           0 :     const float percentage_to_tesla = 0.25f;
     124           0 :     return static_cast<float>(percentage_to_tesla * field_strength * 0.01f);
     125             : }