diff --git a/moving_model/Tramp.c b/moving_model/Tramp.c
index ea26f88..bd5fef3 100644
--- a/moving_model/Tramp.c
+++ b/moving_model/Tramp.c
@@ -122,7 +122,10 @@ static int calc(moveparam_t *x, double t){
         DBG("dx01=%g, dt01=%g", dx01, dt01);
     }else{ // increase or decrease speed without stopping phase
         dt01 = fabs(sign*setspeed - curparams.speed) / Max.accel;
-        double a = (curspeed > setspeed) ? -Max.accel : Max.accel;
+        double a = sign * Max.accel;
+        if(sign * 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 = curspeed * dt01 + a * dt01 * dt01 / 2.;
         DBG("dt01=%g, a=%g, dx01=%g", dt01, a, dx01);
         if(dx01 + dx23 > Dx){ // calculate max speed
@@ -150,7 +153,7 @@ static int calc(moveparam_t *x, double t){
     dx23 = setspeed * dt23 / 2.;
     // calculate dx12 and dt12
     double dx12 = Dx - dx01 - dx23;
-    if(dx12 < 0.){
+    if(dx12 < -coord_tolerance){
         DBG("Oops, WTF?");
         return FALSE;
     }