fix: avoid perpetual movement when the target ang motor position is overshot

3 files changed, 41 insertions, 51 deletions

diff --git a/src/dynamics/solver/joint_constraint/joint_generic_velocity_constraint_builder.rs b/src/dynamics/solver/joint_constraint/joint_generic_velocity_constraint_builder.rs
index 50a37e2..a38f9d3 100644
--- a/src/dynamics/solver/joint_constraint/joint_generic_velocity_constraint_builder.rs
+++ b/src/dynamics/solver/joint_constraint/joint_generic_velocity_constraint_builder.rs
@@ -6,14 +6,13 @@ use crate::dynamics::solver::joint_constraint::{JointVelocityConstraintBuilder,
 use crate::dynamics::solver::MotorParameters;
 use crate::dynamics::{IntegrationParameters, JointIndex, Multibody};
 use crate::math::{Real, Vector, ANG_DIM, DIM, SPATIAL_DIM};
+use crate::utils;
 use crate::utils::IndexMut2;
 use crate::utils::WDot;
 use na::{DVector, SVector};
 
 #[cfg(feature = "dim3")]
 use crate::utils::WAngularInertia;
-#[cfg(feature = "dim2")]
-const PI: Real = std::f64::consts::PI as Real;
 
 impl SolverBody<Real, 1> {
     pub fn fill_jacobians(
@@ -358,7 +357,7 @@ impl JointVelocityConstraintBuilder<Real> {
 
         let s_limits = [(limits[0] / 2.0).sin(), (limits[1] / 2.0).sin()];
         #[cfg(feature = "dim2")]
-        let s_ang = self.ang_err.im;
+        let s_ang = (self.ang_err.angle() / 2.0).sin();
         #[cfg(feature = "dim3")]
         let s_ang = self.ang_err.imag()[limited_axis];
         let min_enabled = s_ang < s_limits[0];
@@ -393,7 +392,7 @@ impl JointVelocityConstraintBuilder<Real> {
     ) -> JointGenericVelocityConstraint {
         // let mut ang_jac = self.ang_basis.column(motor_axis).into_owned();
         #[cfg(feature = "dim2")]
-        let ang_jac = na::Vector1::new(1.0);
+        let ang_jac = na::Vector1::new(1.0); // self.ang_basis[(0, 0)]);
         #[cfg(feature = "dim3")]
         let ang_jac = self.basis.column(_motor_axis).into_owned();
 
@@ -415,18 +414,12 @@ impl JointVelocityConstraintBuilder<Real> {
         let mut rhs_wo_bias = 0.0;
         if motor_params.erp_inv_dt != 0.0 {
             #[cfg(feature = "dim2")]
-            {
-                let s_ang_dist = self.ang_err.angle();
-                let s_target_ang = motor_params.target_pos;
-                rhs_wo_bias += ((s_ang_dist - s_target_ang) % (2.0 * PI)) / (2.0 * PI)
-                    * motor_params.erp_inv_dt;
-            }
+            let s_ang_dist = (self.ang_err.angle() / 2.0).sin();
             #[cfg(feature = "dim3")]
-            {
-                let s_ang_dist = self.ang_err.imag()[_motor_axis];
-                let s_target_ang = motor_params.target_pos.sin();
-                rhs_wo_bias += (s_ang_dist - s_target_ang) * motor_params.erp_inv_dt;
-            }
+            let s_ang_dist = self.ang_err.imag()[_motor_axis];
+            let s_target_ang = (motor_params.target_pos / 2.0).sin();
+            rhs_wo_bias += utils::smallest_abs_diff_between_sin_angles(s_ang_dist, s_target_ang)
+                * motor_params.erp_inv_dt;
         }
 
         let dvel = ang_jac.gdot(body2.angvel) - ang_jac.gdot(body1.angvel);
@@ -746,7 +739,7 @@ impl JointVelocityConstraintBuilder<Real> {
 
         let s_limits = [(limits[0] / 2.0).sin(), (limits[1] / 2.0).sin()];
         #[cfg(feature = "dim2")]
-        let s_ang = self.ang_err.im;
+        let s_ang = (self.ang_err.angle() / 2.0).sin();
         #[cfg(feature = "dim3")]
         let s_ang = self.ang_err.imag()[limited_axis];
         let min_enabled = s_ang < s_limits[0];
@@ -800,18 +793,12 @@ impl JointVelocityConstraintBuilder<Real> {
         let mut rhs = 0.0;
         if motor_params.erp_inv_dt != 0.0 {
             #[cfg(feature = "dim2")]
-            {
-                let s_ang_dist = self.ang_err.angle();
-                let s_target_ang = motor_params.target_pos;
-                rhs += ((s_ang_dist - s_target_ang) % (2.0 * PI)) / (2.0 * PI)
-                    * motor_params.erp_inv_dt;
-            }
+            let s_ang_dist = (self.ang_err.angle() / 2.0).sin();
             #[cfg(feature = "dim3")]
-            {
-                let s_ang_dist = self.ang_err.imag()[_motor_axis];
-                let s_target_ang = motor_params.target_pos.sin();
-                rhs += (s_ang_dist - s_target_ang) * motor_params.erp_inv_dt;
-            }
+            let s_ang_dist = self.ang_err.imag()[_motor_axis];
+            let s_target_ang = (motor_params.target_pos / 2.0).sin();
+            rhs += utils::smallest_abs_diff_between_sin_angles(s_ang_dist, s_target_ang)
+                * motor_params.erp_inv_dt;
         }
 
         let dvel = ang_jac.gdot(body2.angvel) - ang_jac.gdot(body1.angvel);
diff --git a/src/dynamics/solver/joint_constraint/joint_velocity_constraint_builder.rs b/src/dynamics/solver/joint_constraint/joint_velocity_constraint_builder.rs
index 2fae33a..b8b0fe4 100644
--- a/src/dynamics/solver/joint_constraint/joint_velocity_constraint_builder.rs
+++ b/src/dynamics/solver/joint_constraint/joint_velocity_constraint_builder.rs
@@ -5,6 +5,7 @@ use crate::dynamics::solver::joint_constraint::SolverBody;
 use crate::dynamics::solver::MotorParameters;
 use crate::dynamics::{IntegrationParameters, JointIndex, JointLimits};
 use crate::math::{AngVector, Isometry, Matrix, Point, Real, Rotation, Vector, ANG_DIM, DIM};
+use crate::utils;
 use crate::utils::{IndexMut2, WCrossMatrix, WDot, WQuat, WReal};
 use na::SMatrix;
 
@@ -289,7 +290,7 @@ impl<N: WReal> JointVelocityConstraintBuilder<N> {
         let half = N::splat(0.5);
         let s_limits = [(limits[0] * half).simd_sin(), (limits[1] * half).simd_sin()];
         #[cfg(feature = "dim2")]
-        let s_ang = self.ang_err.im;
+        let s_ang = (self.ang_err.angle() * half).simd_sin();
         #[cfg(feature = "dim3")]
         let s_ang = self.ang_err.imag()[limited_axis];
         let min_enabled = s_ang.simd_lt(s_limits[0]);
@@ -353,19 +354,15 @@ impl<N: WReal> JointVelocityConstraintBuilder<N> {
 
         let mut rhs_wo_bias = N::zero();
         if motor_params.erp_inv_dt != N::zero() {
+            let half = N::splat(0.5);
+
             #[cfg(feature = "dim2")]
-            {
-                let s_ang_dist = self.ang_err.angle();
-                let s_target_ang = motor_params.target_pos;
-                rhs_wo_bias += ((s_ang_dist - s_target_ang) % N::simd_two_pi()) / N::simd_two_pi()
-                    * motor_params.erp_inv_dt;
-            }
+            let s_ang_dist = (self.ang_err.angle() * half).simd_sin();
             #[cfg(feature = "dim3")]
-            {
-                let s_ang_dist = self.ang_err.imag()[_motor_axis];
-                let s_target_ang = motor_params.target_pos.simd_sin();
-                rhs_wo_bias += (s_ang_dist - s_target_ang) * motor_params.erp_inv_dt;
-            }
+            let s_ang_dist = self.ang_err.imag()[_motor_axis];
+            let s_target_ang = (motor_params.target_pos * half).simd_sin();
+            rhs_wo_bias += utils::smallest_abs_diff_between_sin_angles(s_ang_dist, s_target_ang)
+                * motor_params.erp_inv_dt;
         }
 
         let dvel = ang_jac.gdot(body2.angvel) - ang_jac.gdot(body1.angvel);
@@ -801,19 +798,15 @@ impl<N: WReal> JointVelocityConstraintBuilder<N> {
 
         let mut rhs_wo_bias = N::zero();
         if motor_params.erp_inv_dt != N::zero() {
+            let half = N::splat(0.5);
+
             #[cfg(feature = "dim2")]
-            {
-                let s_ang_dist = self.ang_err.angle();
-                let s_target_ang = motor_params.target_pos;
-                rhs_wo_bias += ((s_ang_dist - s_target_ang) % N::simd_two_pi()) / N::simd_two_pi()
-                    * motor_params.erp_inv_dt;
-            }
+            let s_ang_dist = (self.ang_err.angle() * half).simd_sin();
             #[cfg(feature = "dim3")]
-            {
-                let s_ang_dist = self.ang_err.imag()[_motor_axis];
-                let s_target_ang = motor_params.target_pos.simd_sin();
-                rhs_wo_bias += (s_ang_dist - s_target_ang) * motor_params.erp_inv_dt;
-            }
+            let s_ang_dist = self.ang_err.imag()[_motor_axis];
+            let s_target_ang = (motor_params.target_pos * half).simd_sin();
+            rhs_wo_bias += utils::smallest_abs_diff_between_sin_angles(s_ang_dist, s_target_ang)
+                * motor_params.erp_inv_dt;
         }
 
         let dvel = ang_jac.gdot(body2.angvel) - ang_jac.gdot(body1.angvel);
@@ -852,7 +845,7 @@ impl<N: WReal> JointVelocityConstraintBuilder<N> {
         let half = N::splat(0.5);
         let s_limits = [(limits[0] * half).simd_sin(), (limits[1] * half).simd_sin()];
         #[cfg(feature = "dim2")]
-        let s_ang = self.ang_err.im;
+        let s_ang = (self.ang_err.angle() * half).simd_sin();
         #[cfg(feature = "dim3")]
         let s_ang = self.ang_err.imag()[limited_axis];
         let min_enabled = s_ang.simd_lt(s_limits[0]);
diff --git a/src/utils.rs b/src/utils.rs
index 4cbc398..90401a4 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -804,3 +804,13 @@ impl<T> IndexMut2<usize> for [T] {
         }
     }
 }
+
+/// Calculate the difference with smallest absolute value between the two given values.
+pub fn smallest_abs_diff_between_sin_angles<N: WReal>(a: N, b: N) -> N {
+    // Select the smallest path among the two angles to reach the target.
+    let s_err = a - b;
+    let sgn = s_err.simd_signum();
+    let s_err_complement = s_err - sgn * N::splat(2.0);
+    let s_err_is_smallest = s_err.simd_abs().simd_lt(s_err_complement.simd_abs());
+    s_err.select(s_err_is_smallest, s_err_complement)
+}