From 062ea78f8fb12b4fc9a2f2df9fced3def0a521f0 Mon Sep 17 00:00:00 2001
From: Filippo Luca Ferretti <filippoluca.ferretti@outlook.com>
Date: Wed, 26 Feb 2025 12:12:33 +0100
Subject: [PATCH] Use vertical asymptote joint viscous friction

---
 src/jaxsim/api/actuation_model.py | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/jaxsim/api/actuation_model.py b/src/jaxsim/api/actuation_model.py
index b6cc2ba1c..96dbb7d28 100644
--- a/src/jaxsim/api/actuation_model.py
+++ b/src/jaxsim/api/actuation_model.py
@@ -83,13 +83,16 @@ def compute_resultant_torques(
 
         ṡ = data.joint_velocities
 
-        v_thresh = 10.0
+        v_thresh = 50.0
 
         # Compute the joint friction torque.
-        τ_friction = -(
-            jnp.diag(kc) @ jnp.sign(ṡ)
-            + jnp.diag(kv) @ (ṡ * v_thresh / (jnp.abs(ṡ) + v_thresh))
-        )
+        # τ_friction = -(
+        #     # jnp.diag(kc) @ jnp.sign(ṡ)
+        #     + jnp.diag(kv) @ (ṡ * v_thresh / (jnp.abs(ṡ) + v_thresh))
+        # )
+
+        # Vertical asymptote
+        τ_friction = -jnp.diag(kv) @ (ṡ / (v_thresh - jnp.abs(ṡ)))
 
     # ===============================
     # Compute the total joint forces.