Bullet Collision Detection & Physics Library
btMultiBodyJointMotor.cpp
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1 /*
2 Bullet Continuous Collision Detection and Physics Library
3 Copyright (c) 2013 Erwin Coumans http://bulletphysics.org
4 
5 This software is provided 'as-is', without any express or implied warranty.
6 In no event will the authors be held liable for any damages arising from the use of this software.
7 Permission is granted to anyone to use this software for any purpose,
8 including commercial applications, and to alter it and redistribute it freely,
9 subject to the following restrictions:
10 
11 1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
12 2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
13 3. This notice may not be removed or altered from any source distribution.
14 */
15 
17 
18 #include "btMultiBodyJointMotor.h"
19 #include "btMultiBody.h"
22 
23 
24 btMultiBodyJointMotor::btMultiBodyJointMotor(btMultiBody* body, int link, btScalar desiredVelocity, btScalar maxMotorImpulse)
25  :btMultiBodyConstraint(body,body,link,body->getLink(link).m_parent,1,true),
26  m_desiredVelocity(desiredVelocity),
27  m_desiredPosition(0),
28  m_kd(1.),
29  m_kp(0),
30  m_erp(1),
31  m_rhsClamp(SIMD_INFINITY)
32 {
33 
34  m_maxAppliedImpulse = maxMotorImpulse;
35  // the data.m_jacobians never change, so may as well
36  // initialize them here
37 
38 
39 }
40 
42 {
44  // note: we rely on the fact that data.m_jacobians are
45  // always initialized to zero by the Constraint ctor
46  int linkDoF = 0;
47  unsigned int offset = 6 + (m_bodyA->getLink(m_linkA).m_dofOffset + linkDoF);
48 
49  // row 0: the lower bound
50  // row 0: the lower bound
51  jacobianA(0)[offset] = 1;
52 
54 }
55 
56 btMultiBodyJointMotor::btMultiBodyJointMotor(btMultiBody* body, int link, int linkDoF, btScalar desiredVelocity, btScalar maxMotorImpulse)
57  //:btMultiBodyConstraint(body,0,link,-1,1,true),
58  :btMultiBodyConstraint(body,body,link,body->getLink(link).m_parent,1,true),
59  m_desiredVelocity(desiredVelocity),
61  m_kd(1.),
62  m_kp(0),
63  m_erp(1),
65 {
66  btAssert(linkDoF < body->getLink(link).m_dofCount);
67 
68  m_maxAppliedImpulse = maxMotorImpulse;
69 
70 }
72 {
73 }
74 
76 {
78  if (col)
79  return col->getIslandTag();
80  for (int i=0;i<m_bodyA->getNumLinks();i++)
81  {
82  if (m_bodyA->getLink(i).m_collider)
83  return m_bodyA->getLink(i).m_collider->getIslandTag();
84  }
85  return -1;
86 }
87 
89 {
91  if (col)
92  return col->getIslandTag();
93 
94  for (int i=0;i<m_bodyB->getNumLinks();i++)
95  {
96  col = m_bodyB->getLink(i).m_collider;
97  if (col)
98  return col->getIslandTag();
99  }
100  return -1;
101 }
102 
103 
106  const btContactSolverInfo& infoGlobal)
107 {
108  // only positions need to be updated -- data.m_jacobians and force
109  // directions were set in the ctor and never change.
110 
112  {
114  }
115 
116  //don't crash
118  return;
119 
120  const btScalar posError = 0;
121  const btVector3 dummy(0, 0, 0);
122 
123  for (int row=0;row<getNumRows();row++)
124  {
125  btMultiBodySolverConstraint& constraintRow = constraintRows.expandNonInitializing();
126 
127  int dof = 0;
128  btScalar currentPosition = m_bodyA->getJointPosMultiDof(m_linkA)[dof];
129  btScalar currentVelocity = m_bodyA->getJointVelMultiDof(m_linkA)[dof];
130  btScalar positionStabiliationTerm = m_erp*(m_desiredPosition-currentPosition)/infoGlobal.m_timeStep;
131 
132  btScalar velocityError = (m_desiredVelocity - currentVelocity);
133  btScalar rhs = m_kp * positionStabiliationTerm + currentVelocity+m_kd * velocityError;
134  if (rhs>m_rhsClamp)
135  {
136  rhs=m_rhsClamp;
137  }
138  if (rhs<-m_rhsClamp)
139  {
140  rhs=-m_rhsClamp;
141  }
142 
143 
144  fillMultiBodyConstraint(constraintRow,data,jacobianA(row),jacobianB(row),dummy,dummy,dummy,dummy,posError,infoGlobal,-m_maxAppliedImpulse,m_maxAppliedImpulse,false,1,false,rhs);
145  constraintRow.m_orgConstraint = this;
146  constraintRow.m_orgDofIndex = row;
147  {
148  //expect either prismatic or revolute joint type for now
151  {
153  {
154  constraintRow.m_contactNormal1.setZero();
155  constraintRow.m_contactNormal2.setZero();
157  constraintRow.m_relpos1CrossNormal=revoluteAxisInWorld;
158  constraintRow.m_relpos2CrossNormal=-revoluteAxisInWorld;
159 
160  break;
161  }
163  {
165  constraintRow.m_contactNormal1=prismaticAxisInWorld;
166  constraintRow.m_contactNormal2=-prismaticAxisInWorld;
167  constraintRow.m_relpos1CrossNormal.setZero();
168  constraintRow.m_relpos2CrossNormal.setZero();
169 
170  break;
171  }
172  default:
173  {
174  btAssert(0);
175  }
176  };
177 
178  }
179 
180  }
181 
182 }
183 
btScalar * jacobianB(int row)
int getNumLinks() const
Definition: btMultiBody.h:155
1D constraint along a normal axis between bodyA and bodyB. It can be combined to solve contact and fr...
const btMultiBodyLinkCollider * getBaseCollider() const
Definition: btMultiBody.h:134
btMultiBodyConstraint * m_orgConstraint
#define btAssert(x)
Definition: btScalar.h:114
btScalar * jacobianA(int row)
btQuaternion getRotation() const
Return a quaternion representing the rotation.
Definition: btTransform.h:122
btScalar * getJointVelMultiDof(int i)
virtual int getIslandIdA() const
btMultiBodyJointMotor(btMultiBody *body, int link, btScalar desiredVelocity, btScalar maxMotorImpulse)
This file was written by Erwin Coumans.
btVector3 quatRotate(const btQuaternion &rotation, const btVector3 &v)
Definition: btQuaternion.h:887
#define SIMD_INFINITY
Definition: btScalar.h:496
void setZero()
Definition: btVector3.h:681
virtual void createConstraintRows(btMultiBodyConstraintArray &constraintRows, btMultiBodyJacobianData &data, const btContactSolverInfo &infoGlobal)
btVector3 can be used to represent 3D points and vectors.
Definition: btVector3.h:83
const btMultibodyLink & getLink(int index) const
Definition: btMultiBody.h:119
int getIslandTag() const
virtual int getIslandIdB() const
btScalar fillMultiBodyConstraint(btMultiBodySolverConstraint &solverConstraint, btMultiBodyJacobianData &data, btScalar *jacOrgA, btScalar *jacOrgB, const btVector3 &constraintNormalAng, const btVector3 &constraintNormalLin, const btVector3 &posAworld, const btVector3 &posBworld, btScalar posError, const btContactSolverInfo &infoGlobal, btScalar lowerLimit, btScalar upperLimit, bool angConstraint=false, btScalar relaxation=1.f, bool isFriction=false, btScalar desiredVelocity=0, btScalar cfmSlip=0)
btScalar * getJointPosMultiDof(int i)
float btScalar
The btScalar type abstracts floating point numbers, to easily switch between double and single floati...
Definition: btScalar.h:279