From bf8fce0269831d2937da5a140a26dc96af35b33e Mon Sep 17 00:00:00 2001
From: Naoki-Hiraoka <hiraoka@jsk.imi.i.u-tokyo.ac.jp>
Date: Sun, 20 Jun 2021 16:44:42 +0900
Subject: [PATCH] [hrplib/hrpModel/ForwardDynamicsCBM.cpp] check equation num
 in solveUnknownAccels

---
 hrplib/hrpModel/ForwardDynamicsCBM.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/hrplib/hrpModel/ForwardDynamicsCBM.cpp b/hrplib/hrpModel/ForwardDynamicsCBM.cpp
index 80b3428d8..8dd062798 100644
--- a/hrplib/hrpModel/ForwardDynamicsCBM.cpp
+++ b/hrplib/hrpModel/ForwardDynamicsCBM.cpp
@@ -707,7 +707,10 @@ void ForwardDynamicsMM::solveUnknownAccels(const Vector3& fext, const Vector3& t
         c1 -= d1;
 	c1 -= b1.col(0);
 
-        dvector a(M11.colPivHouseholderQr().solve(c1));
+        dvector a;
+        if(c1.size()!=0) {
+            a = M11.colPivHouseholderQr().solve(c1);
+        }
 
 	if(unknown_rootDof){
 		Link* root = body->rootLink();