void testRollingOnSurfaceConstraint() { using namespace SimTK; cout << endl; cout << "=================================================================" << endl; cout << " OpenSim RollingOnSurfaceConstraint Simulation " << endl; cout << "=================================================================" << endl; // angle of the rot w.r.t. vertical double theta = -SimTK::Pi / 6; // 30 degs double omega = -2.1234567890; double halfRodLength = 1.0 / (omega*omega); UnitVec3 surfaceNormal(0,1,0); double planeHeight = 0.0; Vec3 comInRod(0, halfRodLength, 0); Vec3 contactPointOnRod(0, 0, 0); double mass = 7.0; SimTK::Inertia inertiaAboutCom = mass*SimTK::Inertia::cylinderAlongY(0.1, 1.0); SimTK::MassProperties rodMass(7.0, comInRod, inertiaAboutCom.shiftFromMassCenter(comInRod, mass)); // Define the Simbody system MultibodySystem system; SimbodyMatterSubsystem matter(system); GeneralForceSubsystem forces(system); SimTK::Force::UniformGravity gravity(forces, matter, gravity_vec); // Create a free joint between the rod and ground MobilizedBody::Planar rod(matter.Ground(), Transform(Vec3(0)), SimTK::Body::Rigid(rodMass), Transform()); // Get underlying mobilized bodies SimTK::MobilizedBody surface = matter.getGround(); // Add a fictitious massless body to be the "Case" reference body coincident with surface for the no-slip constraint SimTK::MobilizedBody::Weld cb(surface, SimTK::Body::Massless()); // Constrain the rod to move on the ground surface SimTK::Constraint::PointInPlane contactY(surface, surfaceNormal, planeHeight, rod, contactPointOnRod); SimTK::Constraint::ConstantAngle contactTorqueAboutY(surface, SimTK::UnitVec3(1, 0, 0), rod, SimTK::UnitVec3(0, 0, 1)); // Constrain the rod to roll on surface and not slide SimTK::Constraint::NoSlip1D contactPointXdir(cb, SimTK::Vec3(0), SimTK::UnitVec3(1, 0, 0), surface, rod); SimTK::Constraint::NoSlip1D contactPointZdir(cb, SimTK::Vec3(0), SimTK::UnitVec3(0, 0, 1), surface, rod); // Simbody model state setup system.realizeTopology(); State state = system.getDefaultState(); //state = system.realizeTopology(); state.updQ()[0] = theta; state.updQ()[1] = 0; state.updQ()[2] = 0; state.updU()[0] = omega; system.realize(state, Stage::Acceleration); state.getUDot().dump("Simbody Accelerations"); Vec3 pcom = system.getMatterSubsystem().calcSystemMassCenterLocationInGround(state); Vec3 vcom = system.getMatterSubsystem().calcSystemMassCenterVelocityInGround(state); Vec3 acom = system.getMatterSubsystem().calcSystemMassCenterAccelerationInGround(state); //========================================================================================================== // Setup OpenSim model Model *osimModel = new Model; osimModel->setGravity(gravity_vec); //OpenSim bodies Ground& ground = osimModel->updGround();; Mesh arrowGeom("arrow.vtp"); arrowGeom.setColor(Vec3(1, 0, 0)); ground.attachGeometry(arrowGeom.clone()); //OpenSim rod auto osim_rod = new OpenSim::Body("rod", mass, comInRod, inertiaAboutCom); OpenSim::PhysicalOffsetFrame* cylFrame = new PhysicalOffsetFrame(*osim_rod, Transform(comInRod)); cylFrame->setName("comInRod"); osimModel->addFrame(cylFrame); Mesh cylGeom("cylinder.vtp"); cylGeom.set_scale_factors(2 * halfRodLength*Vec3(0.1, 1, 0.1)); cylFrame->attachGeometry(cylGeom.clone()); // create rod as a free joint auto rodJoint = new PlanarJoint("rodToGround", ground, *osim_rod); // Add the thigh body which now also contains the hip joint to the model osimModel->addBody(osim_rod); osimModel->addJoint(rodJoint); // add a point on line constraint auto roll = new RollingOnSurfaceConstraint(); roll->setRollingBodyByName("rod"); roll->setSurfaceBodyByName("ground"); /*double h = */roll->get_surface_height(); osimModel->addConstraint(roll); osimModel->setGravity(gravity_vec); //Add analyses before setting up the model for simulation Kinematics *kinAnalysis = new Kinematics(osimModel); kinAnalysis->setInDegrees(false); osimModel->addAnalysis(kinAnalysis); // Need to setup model before adding an analysis since it creates the AnalysisSet // for the model if it does not exist. //osimModel->setUseVisualizer(true); State osim_state = osimModel->initSystem(); roll->setDisabled(osim_state, false); osim_state.updY() = state.getY(); // compute model accelerations osimModel->computeStateVariableDerivatives(osim_state); osim_state.getUDot().dump("Osim Accelerations"); //osimModel->updVisualizer().updSimbodyVisualizer() // .setBackgroundType(SimTK::Visualizer::GroundAndSky); //osimModel->getVisualizer().show(osim_state); Vec3 osim_pcom = osimModel->calcMassCenterPosition(osim_state); Vec3 osim_vcom = osimModel->calcMassCenterVelocity(osim_state); Vec3 osim_acom = osimModel->calcMassCenterAcceleration(osim_state); Vec3 tol(SimTK::SignificantReal); ASSERT_EQUAL(pcom, osim_pcom, tol); ASSERT_EQUAL(vcom, osim_vcom, tol); ASSERT_EQUAL(acom, osim_acom, tol); //========================================================================================================== // Compare Simbody system and OpenSim model simulations compareSimulations(system, state, osimModel, osim_state, "testRollingOnSurfaceConstraint FAILED\n"); }
void testCoordinateCouplerConstraint() { using namespace SimTK; cout << endl; cout << "=================================================================" << endl; cout << " OpenSim CoordinateCouplerConstraint vs. FunctionBasedMobilizer " << endl; cout << "=================================================================" << endl; // Define spline data for the custom knee joint int npx = 12; double angX[] = {-2.094395102393, -1.745329251994, -1.396263401595, -1.047197551197, -0.698131700798, -0.349065850399, -0.174532925199, 0.197344221443, 0.337394955864, 0.490177570472, 1.521460267071, 2.094395102393}; double kneeX[] = {-0.003200000000, 0.001790000000, 0.004110000000, 0.004100000000, 0.002120000000, -0.001000000000, -0.003100000000, -0.005227000000, -0.005435000000, -0.005574000000, -0.005435000000, -0.005250000000}; int npy = 7; double angY[] = {-2.094395102393, -1.221730476396, -0.523598775598, -0.349065850399, -0.174532925199, 0.159148563428, 2.094395102393}; double kneeY[] = {-0.422600000000, -0.408200000000, -0.399000000000, -0.397600000000, -0.396600000000, -0.395264000000, -0.396000000000 }; for(int i = 0; i<npy; i++) { // Spline data points from experiment w.r.t. hip location. Change to make it w.r.t knee location kneeY[i] += (-kneeInFemur[1]+hipInFemur[1]); } SimmSpline tx(npx, angX, kneeX); SimmSpline ty(npy, angY, kneeY);; // Define the functions that specify the FunctionBased Mobilized Body. std::vector<std::vector<int> > coordIndices; std::vector<const SimTK::Function*> functions; std::vector<bool> isdof(6,false); // Set the 1 spatial rotation about Z-axis isdof[2] = true; //rot Z int nm = 0; for(int i=0; i<6; i++){ if(isdof[i]) { Vector coeff(2); coeff[0] = 1; coeff[1] = 0; std::vector<int> findex(1); findex[0] = nm++; functions.push_back(new SimTK::Function::Linear(coeff)); coordIndices.push_back(findex); } else if(i==3 || i ==4){ std::vector<int> findex(1,0); if(i==3) functions.push_back(tx.createSimTKFunction()); else functions.push_back(ty.createSimTKFunction()); coordIndices.push_back(findex); } else{ std::vector<int> findex(0); functions.push_back(new SimTK::Function::Constant(0, 0)); coordIndices.push_back(findex); } } // Define the Simbody system MultibodySystem system; SimbodyMatterSubsystem matter(system); GeneralForceSubsystem forces(system); SimTK::Force::UniformGravity gravity(forces, matter, gravity_vec); //system.updDefaultSubsystem().addEventReporter(new VTKEventReporter(system, 0.01)); // Thigh connected by hip MobilizedBody::Pin thigh(matter.Ground(), Transform(hipInGround), SimTK::Body::Rigid(MassProperties(femurMass, femurCOM, femurInertiaAboutCOM.shiftFromMassCenter(femurCOM, femurMass))), Transform(hipInFemur)); //Function-based knee connects shank MobilizedBody::FunctionBased shank(thigh, Transform(kneeInFemur), SimTK::Body::Rigid(tibiaMass), Transform(kneeInTibia), nm, functions, coordIndices); //MobilizedBody::Pin shank(thigh, SimTK::Transform(kneeInFemur), SimTK::Body::Rigid(tibiaMass), SimTK::Transform(kneeInTibia)); // Simbody model state setup system.realizeTopology(); State state = system.getDefaultState(); matter.setUseEulerAngles(state, true); system.realizeModel(state); //========================================================================================================== // Setup OpenSim model Model *osimModel = new Model; //OpenSim bodies const Ground& ground = osimModel->getGround();; OpenSim::Body osim_thigh("thigh", femurMass, femurCOM, femurInertiaAboutCOM); // create hip as a pin joint PinJoint hip("hip",ground, hipInGround, Vec3(0), osim_thigh, hipInFemur, Vec3(0)); // Rename hip coordinates for a pin joint hip.getCoordinateSet()[0].setName("hip_flex"); // Add the thigh body which now also contains the hip joint to the model osimModel->addBody(&osim_thigh); osimModel->addJoint(&hip); // Add another body via a knee joint OpenSim::Body osim_shank("shank", tibiaMass.getMass(), tibiaMass.getMassCenter(), tibiaMass.getInertia()); // Define knee coordinates and axes for custom joint spatial transform SpatialTransform kneeTransform; string knee_q_name = "knee_q"; string tx_name = "knee_tx"; string ty_name = "knee_ty"; Array<string> indepCoords(knee_q_name, 1, 1); // knee flexion/extension kneeTransform[2].setCoordinateNames(indepCoords); kneeTransform[2].setFunction(new LinearFunction()); // translation X kneeTransform[3].setCoordinateNames(OpenSim::Array<std::string>(tx_name, 1, 1)); kneeTransform[3].setFunction(new LinearFunction()); // translation Y kneeTransform[4].setCoordinateNames(OpenSim::Array<std::string>(ty_name, 1, 1)); kneeTransform[4].setFunction(new LinearFunction()); // create custom knee joint CustomJoint knee("knee", osim_thigh, kneeInFemur, Vec3(0), osim_shank, kneeInTibia, Vec3(0), kneeTransform); // Add the shank body which now also contains the knee joint to the model osimModel->addBody(&osim_shank); osimModel->addJoint(&knee); // Constrain the knee translations to follow the desired manifold CoordinateCouplerConstraint knee_tx_constraint; CoordinateCouplerConstraint knee_ty_constraint; knee_tx_constraint.setName("knee_tx_coupler"); knee_ty_constraint.setName("knee_ty_coupler"); knee_tx_constraint.setIndependentCoordinateNames(indepCoords); knee_ty_constraint.setIndependentCoordinateNames(indepCoords); knee_tx_constraint.setDependentCoordinateName(tx_name); knee_ty_constraint.setDependentCoordinateName(ty_name); knee_tx_constraint.setFunction(tx); knee_ty_constraint.setFunction(ty); // Add the constraints osimModel->addConstraint(&knee_tx_constraint); osimModel->addConstraint(&knee_ty_constraint); //Add analyses before setting up the model for simulation Kinematics *kinAnalysis = new Kinematics(osimModel); kinAnalysis->setInDegrees(false); osimModel->addAnalysis(kinAnalysis); // OpenSim model must realize the topology to get valid osim_state osimModel->setGravity(gravity_vec); PointKinematics *pointKin = new PointKinematics(osimModel); // Get the point location of the shank origin in space pointKin->setBodyPoint("shank", Vec3(0)); osimModel->addAnalysis(pointKin); // Model cannot own model components created on the stack in this test program osimModel->disownAllComponents(); // write out the model to file osimModel->print("testCouplerConstraint.osim"); //wipe-out the model just constructed delete osimModel; // reconstruct from the model file osimModel = new Model("testCouplerConstraint.osim"); ForceReporter *forceReport = new ForceReporter(osimModel); forceReport->includeConstraintForces(true); osimModel->addAnalysis(forceReport); // Need to setup model before adding an analysis since it creates the AnalysisSet // for the model if it does not exist. State& osim_state = osimModel->initSystem(); //========================================================================================================== // Compare Simbody system and OpenSim model simulations compareSimulations(system, state, osimModel, osim_state, "testCoordinateCouplerConstraint FAILED\n"); // Forces were held in storage during simulation, now write to file forceReport->printResults("CouplerModelForces"); }
void testPointOnLineConstraint() { using namespace SimTK; cout << endl; cout << "==================================================================" << endl; cout << "OpenSim PointOnLineConstraint vs. Simbody Constraint::PointOnLine " << endl; cout << "==================================================================" << endl; Random::Uniform randomDirection(-1, 1); Vec3 lineDirection(randomDirection.getValue(), randomDirection.getValue(), randomDirection.getValue()); UnitVec3 normLineDirection(lineDirection.normalize()); Vec3 pointOnLine(0,0,0); Vec3 pointOnFollower(0,0,0); // Define the Simbody system MultibodySystem system; SimbodyMatterSubsystem matter(system); GeneralForceSubsystem forces(system); SimTK::Force::UniformGravity gravity(forces, matter, gravity_vec); // Create a free joint between the foot and ground MobilizedBody::Free foot(matter.Ground(), Transform(Vec3(0)), SimTK::Body::Rigid(footMass), Transform(Vec3(0))); // Constrain foot to line on ground SimTK::Constraint::PointOnLine simtkPointOnLine(matter.Ground(), normLineDirection, pointOnLine, foot, pointOnFollower); // Simbody model state setup system.realizeTopology(); State state = system.getDefaultState(); matter.setUseEulerAngles(state, true); system.realizeModel(state); //========================================================================= // Setup OpenSim model Model *osimModel = new Model; //OpenSim bodies const Ground& ground = osimModel->getGround();; //OpenSim foot OpenSim::Body osim_foot("foot", footMass.getMass(), footMass.getMassCenter(), footMass.getInertia()); // create foot as a free joint FreeJoint footJoint("footToGround", ground, Vec3(0), Vec3(0), osim_foot, Vec3(0), Vec3(0)); // Add the thigh body which now also contains the hip joint to the model osimModel->addBody(&osim_foot); osimModel->addJoint(&footJoint); // add a point on line constraint PointOnLineConstraint lineConstraint(ground, normLineDirection, pointOnLine, osim_foot, pointOnFollower); osimModel->addConstraint(&lineConstraint); // BAD: have to set memoryOwner to false or program will crash when this test is complete. osimModel->disownAllComponents(); osimModel->setGravity(gravity_vec); //Add analyses before setting up the model for simulation Kinematics *kinAnalysis = new Kinematics(osimModel); kinAnalysis->setInDegrees(false); osimModel->addAnalysis(kinAnalysis); // Need to setup model before adding an analysis since it creates the AnalysisSet // for the model if it does not exist. State& osim_state = osimModel->initSystem(); //========================================================================================================== // Compare Simbody system and OpenSim model simulations compareSimulations(system, state, osimModel, osim_state, "testPointOnLineConstraint FAILED\n"); } // end testPointOnLineConstraint
void testWeldConstraint() { using namespace SimTK; cout << endl; cout << "==================================================================" << endl; cout << " OpenSim WeldConstraint vs. Simbody Constraint::Weld " << endl; cout << "==================================================================" << endl; Random::Uniform randomValue(-0.05, 0.1); Vec3 weldInGround(randomValue.getValue(), randomValue.getValue(), 0); Vec3 weldInFoot(0.1*randomValue.getValue(), 0.1*randomValue.getValue(), 0); // Define the Simbody system MultibodySystem system; SimbodyMatterSubsystem matter(system); GeneralForceSubsystem forces(system); SimTK::Force::UniformGravity gravity(forces, matter, gravity_vec); // Thigh connected by hip MobilizedBody::Pin thigh(matter.Ground(), SimTK::Transform(hipInGround), SimTK::Body::Rigid(MassProperties(femurMass, femurCOM, femurInertiaAboutCOM.shiftFromMassCenter(femurCOM, femurMass))), Transform(hipInFemur)); // Pin knee connects shank MobilizedBody::Pin shank(thigh, Transform(kneeInFemur), SimTK::Body::Rigid(tibiaMass), Transform(kneeInTibia)); // Pin ankle connects foot MobilizedBody::Pin foot(shank, Transform(ankleInTibia), SimTK::Body::Rigid(footMass), Transform(ankleInFoot)); SimTK::Constraint::Weld weld(matter.Ground(), Transform(weldInGround), foot, Transform(weldInFoot)); // Simbody model state setup system.realizeTopology(); State state = system.getDefaultState(); matter.setUseEulerAngles(state, true); system.realizeModel(state); //========================================================================================================== // Setup OpenSim model Model *osimModel = new Model; //OpenSim bodies const Ground& ground = osimModel->getGround();; //OpenSim thigh OpenSim::Body osim_thigh("thigh", femurMass, femurCOM, femurInertiaAboutCOM); // create Pin hip joint PinJoint hip("hip", ground, hipInGround, Vec3(0), osim_thigh, hipInFemur, Vec3(0)); // Add the thigh body which now also contains the hip joint to the model osimModel->addBody(&osim_thigh); osimModel->addJoint(&hip); //OpenSim shank OpenSim::Body osim_shank("shank", tibiaMass.getMass(), tibiaMass.getMassCenter(), tibiaMass.getInertia()); // create Pin knee joint PinJoint knee("knee", osim_thigh, kneeInFemur, Vec3(0), osim_shank, kneeInTibia, Vec3(0)); // Add the thigh body which now also contains the hip joint to the model osimModel->addBody(&osim_shank); osimModel->addJoint(&knee); //OpenSim foot OpenSim::Body osim_foot("foot", footMass.getMass(), footMass.getMassCenter(), footMass.getInertia()); // create Pin ankle joint PinJoint ankle("ankle", osim_shank, ankleInTibia, Vec3(0), osim_foot, ankleInFoot, Vec3(0)); // Add the foot body which now also contains the hip joint to the model osimModel->addBody(&osim_foot); osimModel->addJoint(&ankle); // add a point on line constraint WeldConstraint footConstraint( "footConstraint", ground, SimTK::Transform(weldInGround), osim_foot, SimTK::Transform(weldInFoot) ); osimModel->addConstraint(&footConstraint); // BAD: but if model maintains ownership, it will attempt to delete stack allocated objects osimModel->disownAllComponents(); osimModel->setGravity(gravity_vec); //Add analyses before setting up the model for simulation Kinematics *kinAnalysis = new Kinematics(osimModel); kinAnalysis->setInDegrees(false); osimModel->addAnalysis(kinAnalysis); osimModel->setup(); osimModel->print("testWeldConstraint.osim"); // Need to setup model before adding an analysis since it creates the AnalysisSet // for the model if it does not exist. State& osim_state = osimModel->initSystem(); //========================================================================= // Compare Simbody system and OpenSim model simulations compareSimulations(system, state, osimModel, osim_state, "testWeldConstraint FAILED\n"); }
void testConstantDistanceConstraint() { using namespace SimTK; cout << endl; cout << "==================================================================" << endl; cout << " OpenSim ConstantDistanceConstraint vs. Simbody Constraint::Rod " << endl; cout << "==================================================================" << endl; Random::Uniform randomLocation(-1, 1); Vec3 pointOnFoot(randomLocation.getValue(), randomLocation.getValue(), randomLocation.getValue()); Vec3 pointOnGround(0,0,0); /** for some reason, adding another Random::Uniform causes testWeldConstraint to fail. Why doesn't it cause this test to fail???? */ //Random::Uniform randomLength(0.01, 0.2); //randomLength.setSeed(1024); //double rodLength = randomLength.getValue(); double rodLength = 0.05; //std::cout << "Random Length = " << rodLength2 << ", used length = " << rodLength << std::endl; // Define the Simbody system MultibodySystem system; SimbodyMatterSubsystem matter(system); GeneralForceSubsystem forces(system); SimTK::Force::UniformGravity gravity(forces, matter, gravity_vec); // Create a free joint between the foot and ground MobilizedBody::Free foot(matter.Ground(), Transform(Vec3(0)), SimTK::Body::Rigid(footMass), Transform(Vec3(0))); // Constrain foot to point on ground SimTK::Constraint::Rod simtkRod(matter.Ground(), pointOnGround, foot, pointOnFoot, rodLength); // Simbody model state setup system.realizeTopology(); State state = system.getDefaultState(); matter.setUseEulerAngles(state, true); system.realizeModel(state); //========================================================================================================== // Setup OpenSim model Model *osimModel = new Model; //OpenSim bodies const Ground& ground = osimModel->getGround();; //OpenSim foot OpenSim::Body osim_foot("foot", footMass.getMass(), footMass.getMassCenter(), footMass.getInertia()); // create foot as a free joint FreeJoint footJoint("footToGround", ground, Vec3(0), Vec3(0), osim_foot, Vec3(0), Vec3(0)); // Add the thigh body which now also contains the hip joint to the model osimModel->addBody(&osim_foot); osimModel->addJoint(&footJoint); // add a constant distance constraint ConstantDistanceConstraint rodConstraint(ground, pointOnGround, osim_foot, pointOnFoot,rodLength); osimModel->addConstraint(&rodConstraint); // BAD: have to set memoryOwner to false or program will crash when this test is complete. osimModel->disownAllComponents(); osimModel->setGravity(gravity_vec); //Add analyses before setting up the model for simulation Kinematics *kinAnalysis = new Kinematics(osimModel); kinAnalysis->setInDegrees(false); osimModel->addAnalysis(kinAnalysis); // Need to setup model before adding an analysis since it creates the AnalysisSet // for the model if it does not exist. State& osim_state = osimModel->initSystem(); //========================================================================================================== // Compare Simbody system and OpenSim model simulations compareSimulations(system, state, osimModel, osim_state, "testConstantDistanceConstraint FAILED\n"); }
void testExternalLoad() { using namespace SimTK; Model model("Pendulum.osim"); State &s = model.initSystem(); // Simulate gravity double init_t =-1e-8; double final_t = 2.0; int nsteps = 10; double dt = final_t/nsteps; //initial state double q_init = Pi/4; model.updCoordinateSet()[0].setValue(s, q_init); Vector_<double> q_grav(nsteps+1); // Integrator and integration manager double integ_accuracy = 1e-6; RungeKuttaMersonIntegrator integrator(model.getMultibodySystem() ); integrator.setAccuracy(integ_accuracy); Manager manager(model, integrator); manager.setInitialTime(init_t); for(int i = 0; i < nsteps+1; i++){ manager.setFinalTime(dt*i); manager.integrate(s); q_grav[i] = model.updCoordinateSet()[0].getValue(s); manager.setInitialTime(dt*i); } //q_grav.dump("Coords due to gravity."); /***************************** CASE 1 ************************************/ // Simulate the same system without gravity but with an equivalent external load OpenSim::Body &pendulum = model.getBodySet().get(model.getNumBodies()-1); string pendBodyName = pendulum.getName(); Vec3 comInB = pendulum.getMassCenter(); Storage forceStore; addLoadToStorage(forceStore, pendulum.getMass()*model.getGravity(), comInB, Vec3(0, 0, 0)); forceStore.setName("test_external_loads.sto"); forceStore.print(forceStore.getName()); // Apply external force with force in ground, point in body, zero torque ExternalForce xf(forceStore, "force", "point", "torque", pendBodyName, "ground", pendBodyName); xf.setName("grav"); ExternalLoads* extLoads = new ExternalLoads(model); extLoads->adoptAndAppend(&xf); extLoads->print("ExternalLoads_test.xml"); for(int i=0; i<extLoads->getSize(); i++) model.addForce(&(*extLoads)[i]); // Create the force reporter ForceReporter* reporter = new ForceReporter(); model.addAnalysis(reporter); Kinematics* kin = new Kinematics(); kin->setInDegrees(false); model.addAnalysis(kin); PointKinematics* pKin = new PointKinematics(); pKin->setBody(&pendulum); pKin->setPoint(comInB); pKin->setPointName(pendulum.getName()+"_com_p"); model.addAnalysis(pKin); SimTK::State& s2 = model.initSystem(); // Turn-off gravity in the model model.updGravityForce().disable(s2); // initial position model.updCoordinateSet()[0].setValue(s2, q_init); RungeKuttaMersonIntegrator integrator2(model.getMultibodySystem() ); integrator2.setAccuracy(integ_accuracy); Manager manager2(model, integrator2); manager2.setInitialTime(init_t); // Simulate with the external force applied instead of gravity Vector_<double> q_xf(nsteps+1); Vector_<Vec3> pcom_xf(nsteps+1); for(int i = 0; i < nsteps+1; i++){ manager2.setFinalTime(dt*i); manager2.integrate(s2); q_xf[i] = model.updCoordinateSet()[0].getValue(s2); manager2.setInitialTime(dt*i); } //q_xf.dump("Coords due to external force point expressed in pendulum."); Vector err = q_xf-q_grav; double norm_err = err.norm(); // kinematics should match to within integ accuracy ASSERT_EQUAL(0.0, norm_err, integ_accuracy); /***************************** CASE 2 ************************************/ // Simulate the same system without gravity but with an equivalent external // force but this time with the point expressed in ground and using // previous kinematics to transform point to pendulum. // Construct a new Storage for ExternalForce data source with point // described in ground Storage forceStore2 = reporter->getForceStorage(); forceStore2.print("ForcesTest.sto"); Storage *pStore = pKin->getPositionStorage(); pStore->print("PointInGroundTest.sto"); pStore->addToRdStorage(forceStore2, init_t, final_t); forceStore2.setName("ExternalForcePointInGround.sto"); forceStore2.print(forceStore2.getName()); Storage *qStore = kin->getPositionStorage(); qStore->print("LoadKinematics.sto"); string id_base = pendBodyName+"_"+xf.getName(); string point_id = pKin->getPointName(); ExternalForce xf2(forceStore2, id_base+"_F", point_id, id_base+"_T", pendBodyName, "ground", "ground"); xf2.setName("xf_pInG"); // Empty out existing external forces extLoads->setMemoryOwner(false); extLoads->setSize(0); extLoads->adoptAndAppend(&xf2); //Ask external loads to transform point expressed in ground to the applied body extLoads->setDataFileName(forceStore2.getName()); extLoads->invokeConnectToModel(model); extLoads->transformPointsExpressedInGroundToAppliedBodies(*qStore); // remove previous external force from the model too model.disownAllComponents(); model.updForceSet().setSize(0); // after external loads has transformed the point of the force, then add it the model for(int i=0; i<extLoads->getSize(); i++) model.addForce(&(*extLoads)[i]); // recreate dynamical system to reflect new force SimTK::State &s3 = model.initSystem(); // Turn-off gravity in the model model.updGravityForce().disable(s3); // initial position model.updCoordinateSet()[0].setValue(s3, q_init); RungeKuttaMersonIntegrator integrator3(model.getMultibodySystem() ); integrator3.setAccuracy(integ_accuracy); Manager manager3(model, integrator3); manager3.setInitialTime(init_t); // Simulate with the external force applied instead of gravity Vector_<double> q_xf2(nsteps+1); for(int i = 0; i < nsteps+1; i++){ manager3.setFinalTime(dt*i); manager3.integrate(s3); q_xf2[i] = model.updCoordinateSet()[0].getValue(s3); manager3.setInitialTime(dt*i); } //q_xf2.dump("Coords due to external force point expressed in ground."); err = q_xf2-q_grav; //err.dump("Coordinate error after transforming point."); norm_err = err.norm(); // kinematics should match to within integ accuracy ASSERT_EQUAL(0.0, norm_err, integ_accuracy); }