mountcontrol/LibSidServo/ramp.c

/*
 * This file is part of the moving_model project.
 * Copyright 2025 Edward V. Emelianov <edward.emelianoff@gmail.com>.
 *
 * 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/>.
 */

// simplest trapezioidal ramp

#include <math.h>
#include <strings.h>

#include "main.h"
#include "ramp.h"

static double coord_tolerance = COORD_TOLERANCE_DEFAULT;

static void emstop(movemodel_t *m, double _U_ t){
    FNAME();
    pthread_mutex_lock(&m->mutex);
    m->curparams.accel = 0.;
    m->curparams.speed = 0.;
    bzero(m->Times, sizeof(double) * STAGE_AMOUNT);
    bzero(m->Params, sizeof(moveparam_t) * STAGE_AMOUNT);
    m->state = ST_STOP;
    m->movingstage = STAGE_STOPPED;
    pthread_mutex_unlock(&m->mutex);
}

static void stop(movemodel_t *m, double t){
    FNAME();
    pthread_mutex_lock(&m->mutex);
    if(m->state == ST_STOP || m->movingstage == STAGE_STOPPED) goto ret;
    m->movingstage = STAGE_DECEL;
    m->state = ST_MOVE;
    m->Times[STAGE_DECEL] = t;
    m->Params[STAGE_DECEL].speed = m->curparams.speed;
    if(m->curparams.speed > 0.) m->Params[STAGE_DECEL].accel = -m->Max.accel;
    else m->Params[STAGE_DECEL].accel = m->Max.accel;
    m->Params[STAGE_DECEL].coord = m->curparams.coord;
    // speed: v=v2+a2(t-t2), v2 and a2 have different signs; t3: v3=0 -> t3=t2-v2/a2
    m->Times[STAGE_STOPPED] = t - m->curparams.speed / m->Params[STAGE_DECEL].accel;
    // coordinate: x=x2+v2(t-t2)+a2(t-t2)^2/2 -> x3=x2+v2(t3-t2)+a2(t3-t2)^2/2
    double dt = m->Times[STAGE_STOPPED] - t;
    m->Params[STAGE_STOPPED].coord = m->curparams.coord + m->curparams.speed * dt +
                                  m->Params[STAGE_DECEL].accel * dt * dt / 2.;
ret:
    pthread_mutex_unlock(&m->mutex);
}

/**
 * @brief calc - moving calculation
 * @param x - using max speed (>0!!!) and coordinate
 * @param t - current time value
 * @return FALSE if can't move with given parameters
 */
static int calc(movemodel_t *m, moveparam_t *x, double t){
    DBG("coord/speed: %g/%g", x->coord, x->speed);
    if(!x) return FALSE;
    pthread_mutex_lock(&m->mutex);
    int ret = FALSE;
    if(x->coord < m->Min.coord || x->coord > m->Max.coord){
        DBG("Wrong coordinage [%g, %g]", m->Min.coord, m->Max.coord);
        goto ret;
    }
    if(x->speed < m->Min.speed || x->speed > m->Max.speed){
        DBG("Wrong speed [%g, %g]", m->Min.speed, m->Max.speed);
        goto ret;
    }
    double Dx = fabs(x->coord - m->curparams.coord); // full distance
    double sign = (x->coord > m->curparams.coord) ? 1. : -1.; // sign of target accelerations and speeds
    // we have two variants: with or without stage with constant speed
    double dt23 = x->speed / m->Max.accel; // time of deceleration stage for given speed
    double dx23 = x->speed * dt23 / 2.; // distance on dec stage (abs)
    DBG("Dx=%g, sign=%g, dt23=%g, dx23=%g", Dx, sign, dt23, dx23);
    double setspeed = x->speed; // new max speed (we can change it if need)
    double dt01, dx01; // we'll fill them depending on starting conditions
    m->Times[0] = t;
    m->Params[0].speed = m->curparams.speed;
    m->Params[0].coord = m->curparams.coord;

    double curspeed = fabs(m->curparams.speed);
    double dt0s = curspeed / m->Max.accel; // time of stopping phase
    double dx0s = curspeed * dt0s / 2.; // distance
    DBG("dt0s=%g, dx0s=%g, curspeed=%g", dt0s, dx0s, curspeed);
    if(fabs(Dx - dx0s) < coord_tolerance){ // just stop and we'll be on target
        DBG("Distance good to just stop");
        pthread_mutex_unlock(&m->mutex);
        stop(m, t);
        ret = TRUE;
        goto ret;
    }
    if(m->curparams.speed * sign < 0. || m->state == ST_STOP || (dx0s > Dx + coord_tolerance)){ // we should change speed sign
        DBG("SIGN of speed should be changed!");
        double sign_current = (m->curparams.speed >= 0.) ? 1. : -1.;
        if (m->state == ST_STOP) {
            // Already stopped
            dx0s = 0.;
            sign_current = 0.;
        }
        double stop_coord = m->curparams.coord + sign_current * dx0s;
        double Dx_after = fabs(x->coord - stop_coord);
        double sign_after = (x->coord > stop_coord) ? 1. : -1.;

        // Calculate new max speed for reverse movement
        double setspeed = sqrt(m->Max.accel * Dx_after);
        if (setspeed > x->speed) setspeed = x->speed;
        if (setspeed > m->Max.speed) setspeed = m->Max.speed;
        if (setspeed < m->Min.speed) {
            DBG("New speed (%g) too small (<%g)", setspeed, m->Min.speed);
            goto ret;
        }

        double t_acc = setspeed / m->Max.accel;

        // Stage 0: Stop current movement (if moving)
        m->Times[STAGE_ACCEL] = t;
        m->Params[STAGE_ACCEL].coord = m->curparams.coord;
        m->Params[STAGE_ACCEL].speed = m->curparams.speed;
        if (m->state != ST_STOP) {
            m->Params[STAGE_ACCEL].accel = -sign_current * m->Max.accel;
            m->Times[STAGE_MAXSPEED] = t + dt0s;
        } else {
            m->Params[STAGE_ACCEL].accel = 0.;
            m->Times[STAGE_MAXSPEED] = t;
        }

        // Stage 1: Accelerate in opposite direction
        m->Params[STAGE_MAXSPEED].coord = stop_coord;
        m->Params[STAGE_MAXSPEED].speed = 0.;
        m->Params[STAGE_MAXSPEED].accel = sign_after * m->Max.accel;
        m->Times[STAGE_DECEL] = m->Times[STAGE_MAXSPEED] + t_acc;
        m->Params[STAGE_DECEL].coord = stop_coord + sign_after * (0.5 * m->Max.accel * t_acc * t_acc);
        m->Params[STAGE_DECEL].speed = sign_after * setspeed;
        m->Params[STAGE_DECEL].accel = -sign_after * m->Max.accel;

        // Stage 2: Decelerate to stop at target
        m->Times[STAGE_STOPPED] = m->Times[STAGE_DECEL] + t_acc;
        m->Params[STAGE_STOPPED].coord = x->coord;
        m->Params[STAGE_STOPPED].speed = 0.;
        m->Params[STAGE_STOPPED].accel = 0.;

        ret = TRUE;
        goto ret;
    }else{ // increase or decrease speed without stopping phase
        dt01 = fabs(sign*setspeed - m->curparams.speed) / m->Max.accel;
        double a = sign * m->Max.accel;
        if(sign * m->curparams.speed < 0.){DBG("change direction"); a = -a;}
        else if(curspeed > setspeed){ DBG("lower speed @ this direction"); a = -a;}
        //double a = (curspeed > setspeed) ? -Max.accel : Max.accel;
        dx01 = sign*(curspeed * dt01 + a * dt01 * dt01 / 2.);
        DBG("dt01=%g, a=%g, dx01=%g", dt01, a, dx01);
        if(dx01 + dx23 > Dx){ // calculate max speed
            setspeed = sqrt(m->Max.accel * Dx - curspeed * curspeed / 2.);
            if(setspeed < curspeed){
                setspeed = curspeed;
                dt01 = 0.; dx01 = 0.;
                m->Params[0].accel = 0.;
            }else{
                m->Params[0].accel = a;
                dt01 = fabs(setspeed - curspeed) / m->Max.accel;
                dx01 = curspeed * dt01 + m->Max.accel * dt01 * dt01 / 2.;
            }
        }else m->Params[0].accel = a;
    }
    if(setspeed < m->Min.speed){
        DBG("New speed (%g) should be too small (<%g)", setspeed, m->Min.speed);
        goto ret;
    }
    moveparam_t *p = &m->Params[STAGE_MAXSPEED];
    p->accel = 0.; p->speed = sign * setspeed;
    p->coord = m->curparams.coord + dx01 * sign;
    m->Times[STAGE_MAXSPEED] = m->Times[0] + dt01;
    dt23 = setspeed / m->Max.accel;
    dx23 = setspeed * dt23 / 2.;
    DBG("setspeed=%g, dt23=%g, tx23=%g", setspeed, dt23, dx23);
    // calculate dx12 and dt12
    double dx12 = Dx - dx01 - dx23;
    if(dx12 < -coord_tolerance){
        DBG("Oops, WTF dx12=%g?", dx12);
        goto ret;
    }
    double dt12 = dx12 / setspeed;
    p = &m->Params[STAGE_DECEL];
    p->accel = -sign * m->Max.accel;
    p->speed = sign * setspeed;
    p->coord = m->Params[STAGE_MAXSPEED].coord + sign * dx12;
    m->Times[STAGE_DECEL] = m->Times[STAGE_MAXSPEED] + dt12;
    p = &m->Params[STAGE_STOPPED];
    p->accel = 0.; p->speed = 0.; p->coord = x->coord;
    m->Times[STAGE_STOPPED] = m->Times[STAGE_DECEL] + dt23;
    ret = TRUE;
ret:
    if(ret){
        m->state = ST_MOVE;
        m->movingstage = STAGE_ACCEL;
        for(int i = 0; i < 4; ++i)
            DBG("%d: t=%g, coord=%g, speed=%g, accel=%g", i,
                m->Times[i], m->Params[i].coord, m->Params[i].speed, m->Params[i].accel);
    }
    pthread_mutex_unlock(&m->mutex);
    return ret;
}

static movestate_t proc(movemodel_t *m, moveparam_t *next, double t){
    pthread_mutex_lock(&m->mutex);
    if(m->state == ST_STOP) goto ret;
    for(movingstage_t s = STAGE_STOPPED; s >= 0; --s){
        if(m->Times[s] <= t){ // check time for current stage
            m->movingstage = s;
            break;
        }
    }
    if(m->movingstage == STAGE_STOPPED){
        m->curparams.coord = m->Params[STAGE_STOPPED].coord;
        pthread_mutex_unlock(&m->mutex);
        emstop(m, t);
        goto ret;
    }
    // calculate current parameters
    double dt = t - m->Times[m->movingstage];
    double a = m->Params[m->movingstage].accel;
    double v0 = m->Params[m->movingstage].speed;
    double x0 = m->Params[m->movingstage].coord;
    m->curparams.accel = a;
    m->curparams.speed = v0 + a * dt;
    m->curparams.coord = x0 + v0 * dt + a * dt * dt / 2.;
ret:
    if(next) *next = m->curparams;
    movestate_t st = m->state;
    pthread_mutex_unlock(&m->mutex);
    return st;
}

static movestate_t getst(movemodel_t *m, moveparam_t *cur){
    pthread_mutex_lock(&m->mutex);
    if(cur) *cur = m->curparams;
    movestate_t st = m->state;
    pthread_mutex_unlock(&m->mutex);
    return st;
}

static double gettstop(movemodel_t *m){
    pthread_mutex_lock(&m->mutex);
    double r = m->Times[STAGE_STOPPED];
    pthread_mutex_unlock(&m->mutex);
    return r;
}

movemodel_t trapez = {
    .stop = stop,
    .emergency_stop = emstop,
    .get_state = getst,
    .calculate = calc,
    .proc_move = proc,
    .stoppedtime = gettstop,
};