Exemple #1
0
// -----------------------------------------------------------------------------
// Calculate kinematics quantities (slip angle, longitudinal slip, camber angle,
// and toe-in angle using the current state of the associated wheel body.
// -----------------------------------------------------------------------------
void ChTire::CalculateKinematics(double time, const WheelState& state, const ChTerrain& terrain) {
    // Wheel normal (expressed in global frame)
    ChVector<> wheel_normal = state.rot.GetYaxis();

    // Terrain normal at wheel location (expressed in global frame)
    ChVector<> Z_dir = terrain.GetNormal(state.pos.x(), state.pos.y());

    // Longitudinal (heading) and lateral directions, in the terrain plane
    ChVector<> X_dir = Vcross(wheel_normal, Z_dir);
    X_dir.Normalize();
    ChVector<> Y_dir = Vcross(Z_dir, X_dir);

    // Tire reference coordinate system
    ChMatrix33<> rot;
    rot.Set_A_axis(X_dir, Y_dir, Z_dir);
    ChCoordsys<> tire_csys(state.pos, rot.Get_A_quaternion());

    // Express wheel linear velocity in tire frame
    ChVector<> V = tire_csys.TransformDirectionParentToLocal(state.lin_vel);
    // Express wheel normal in tire frame
    ChVector<> n = tire_csys.TransformDirectionParentToLocal(wheel_normal);

    // Slip angle
    double abs_Vx = std::abs(V.x());
    double zero_Vx = 1e-4;
    m_slip_angle = (abs_Vx > zero_Vx) ? std::atan(V.y() / abs_Vx) : 0;

    // Longitudinal slip
    m_longitudinal_slip = (abs_Vx > zero_Vx) ? -(V.x() - state.omega * GetRadius()) / abs_Vx : 0;

    // Camber angle
    m_camber_angle = std::atan2(n.z(), n.y());
}
double ChCollisionUtils::PointTriangleDistance(Vector B,
                                               Vector A1,
                                               Vector A2,
                                               Vector A3,
                                               double& mu,
                                               double& mv,
                                               int& is_into,
                                               Vector& Bprojected) {
    // defaults
    is_into = 0;
    mu = mv = -1;
    double mdistance = 10e22;

    Vector Dx, Dy, Dz, T1, T1p;

    Dx = Vsub(A2, A1);
    Dz = Vsub(A3, A1);
    Dy = Vcross(Dz, Dx);

    double dylen = Vlength(Dy);

    if (fabs(dylen) < EPS_TRIDEGEN)  // degenerate triangle
        return mdistance;

    Dy = Vmul(Dy, 1.0 / dylen);

    ChMatrix33<> mA;
    ChMatrix33<> mAi;
    mA.Set_A_axis(Dx, Dy, Dz);

    // invert triangle coordinate matrix -if singular matrix, was degenerate triangle-.
    if (fabs(mA.FastInvert(mAi)) < 0.000001)
        return mdistance;

    T1 = mAi.Matr_x_Vect(Vsub(B, A1));
    T1p = T1;
    T1p.y() = 0;
    mu = T1.x();
    mv = T1.z();
    mdistance = -T1.y();
    if (mu >= 0 && mv >= 0 && mv <= 1.0 - mu) {
        is_into = 1;
        Bprojected = Vadd(A1, mA.Matr_x_Vect(T1p));
    }

    return mdistance;
}
Exemple #3
0
// -----------------------------------------------------------------------------
// Utility function for characterizing the geometric contact between a disc with
// specified center location, normal direction, and radius and the terrain,
// assumed to be specified as a height field (over the x-y domain).
// This function returns false if no contact occurs. Otherwise, it sets the
// contact points on the disc (ptD) and on the terrain (ptT), the normal contact
// direction, and the resulting penetration depth (a positive value).
// -----------------------------------------------------------------------------
bool ChTire::disc_terrain_contact(const ChTerrain& terrain,
                                  const ChVector<>& disc_center,
                                  const ChVector<>& disc_normal,
                                  double disc_radius,
                                  ChCoordsys<>& contact,
                                  double& depth) {
    // Find terrain height below disc center. There is no contact if the disc
    // center is below the terrain or farther away by more than its radius.
    double hc = terrain.GetHeight(disc_center.x(), disc_center.y());
    if (disc_center.z() <= hc || disc_center.z() >= hc + disc_radius)
        return false;

    // Find the lowest point on the disc. There is no contact if the disc is
    // (almost) horizontal.
    ChVector<> dir1 = Vcross(disc_normal, ChVector<>(0, 0, 1));
    double sinTilt2 = dir1.Length2();

    if (sinTilt2 < 1e-3)
        return false;

    // Contact point (lowest point on disc).
    ChVector<> ptD = disc_center + disc_radius * Vcross(disc_normal, dir1 / sqrt(sinTilt2));

    // Find terrain height at lowest point. No contact if lowest point is above
    // the terrain.
    double hp = terrain.GetHeight(ptD.x(), ptD.y());

    if (ptD.z() > hp)
        return false;

    // Approximate the terrain with a plane. Define the projection of the lowest
    // point onto this plane as the contact point on the terrain.
    ChVector<> normal = terrain.GetNormal(ptD.x(), ptD.y());
    ChVector<> longitudinal = Vcross(disc_normal, normal);
    longitudinal.Normalize();
    ChVector<> lateral = Vcross(normal, longitudinal);
    ChMatrix33<> rot;
    rot.Set_A_axis(longitudinal, lateral, normal);

    contact.pos = ptD;
    contact.rot = rot.Get_A_quaternion();

    depth = Vdot(ChVector<>(0, 0, hp - ptD.z()), normal);
    assert(depth > 0);

    return true;
}
// -----------------------------------------------------------------------------
// -----------------------------------------------------------------------------
void ChLinearDamperRWAssembly::Initialize(std::shared_ptr<ChBodyAuxRef> chassis, const ChVector<>& location) {
    // Express the suspension reference frame in the absolute coordinate system.
    ChFrame<> susp_to_abs(location);
    susp_to_abs.ConcatenatePreTransformation(chassis->GetFrame_REF_to_abs());

    // Transform all points and directions to absolute frame.
    std::vector<ChVector<> > points(NUM_POINTS);

    for (int i = 0; i < NUM_POINTS; i++) {
        ChVector<> rel_pos = GetLocation(static_cast<PointId>(i));
        points[i] = susp_to_abs.TransformPointLocalToParent(rel_pos);
    }

    // Create the trailing arm body. The reference frame of the arm body has its
    // x-axis aligned with the line between the arm-chassis connection point and
    // the arm-wheel connection point.
    ChVector<> y_dir = susp_to_abs.GetA().Get_A_Yaxis();
    ChVector<> u = susp_to_abs.GetPos() - points[ARM_CHASSIS];
    u.Normalize();
    ChVector<> w = Vcross(u, y_dir);
    w.Normalize();
    ChVector<> v = Vcross(w, u);
    ChMatrix33<> rot;
    rot.Set_A_axis(u, v, w);

    m_arm = std::shared_ptr<ChBody>(chassis->GetSystem()->NewBody());
    m_arm->SetNameString(m_name + "_arm");
    m_arm->SetPos(points[ARM]);
    m_arm->SetRot(rot);
    m_arm->SetMass(GetArmMass());
    m_arm->SetInertiaXX(GetArmInertia());
    chassis->GetSystem()->AddBody(m_arm);

    // Cache points and directions for arm visualization (expressed in the arm frame)
    m_pO = m_arm->TransformPointParentToLocal(susp_to_abs.GetPos());
    m_pA = m_arm->TransformPointParentToLocal(points[ARM]);
    m_pAW = m_arm->TransformPointParentToLocal(points[ARM_WHEEL]);
    m_pAC = m_arm->TransformPointParentToLocal(points[ARM_CHASSIS]);
    m_pAS = m_arm->TransformPointParentToLocal(points[SHOCK_A]);
    m_dY = m_arm->TransformDirectionParentToLocal(y_dir);

    // Create and initialize the revolute joint between arm and chassis.
    // The axis of rotation is the y axis of the suspension reference frame.
    m_revolute = std::make_shared<ChLinkLockRevolute>();
    m_revolute->SetNameString(m_name + "_revolute");
    m_revolute->Initialize(chassis, m_arm,
                           ChCoordsys<>(points[ARM_CHASSIS], susp_to_abs.GetRot() * Q_from_AngX(CH_C_PI_2)));
    chassis->GetSystem()->AddLink(m_revolute);

    // Create and initialize the rotational spring torque element.
    m_spring = std::make_shared<ChLinkRotSpringCB>();
    m_spring->SetNameString(m_name + "_spring");
    m_spring->Initialize(chassis, m_arm, ChCoordsys<>(points[ARM_CHASSIS], susp_to_abs.GetRot() * Q_from_AngX(CH_C_PI_2)));
    m_spring->RegisterTorqueFunctor(GetSpringTorqueFunctor());
    chassis->GetSystem()->AddLink(m_spring);

    // Create and initialize the translational shock force element.
    if (m_has_shock) {
        m_shock = std::make_shared<ChLinkSpringCB>();
        m_shock->SetNameString(m_name + "_shock");
        m_shock->Initialize(chassis, m_arm, false, points[SHOCK_C], points[SHOCK_A]);
        m_shock->RegisterForceFunctor(GetShockForceFunctor());
        chassis->GetSystem()->AddLink(m_shock);
    }

    // Invoke the base class implementation. This initializes the associated road wheel.
    // Note: we must call this here, after the m_arm body is created.
    ChRoadWheelAssembly::Initialize(chassis, location);
}
Exemple #5
0
void ChLinkPulley::UpdateTime (double mytime)
{
    // First, inherit to parent class
    ChLinkLock::UpdateTime(mytime);

	ChFrame<double> abs_shaft1;
	ChFrame<double> abs_shaft2;

	((ChFrame<double>*)Body1)->TrasformLocalToParent(local_shaft1, abs_shaft1);
	((ChFrame<double>*)Body2)->TrasformLocalToParent(local_shaft2, abs_shaft2);

	ChVector<> dcc_w = Vsub(Get_shaft_pos2(),
                            Get_shaft_pos1());

		// compute actual rotation of the two wheels (relative to truss).
    Vector md1 = abs_shaft1.GetA()->MatrT_x_Vect(dcc_w);
    md1.z = 0;  md1 = Vnorm (md1);
    Vector md2 = abs_shaft2.GetA()->MatrT_x_Vect(dcc_w);
    md2.z = 0;  md2 = Vnorm (md2);

	double periodic_a1 = ChAtan2(md1.x, md1.y);
	double periodic_a2 = ChAtan2(md2.x, md2.y);
	double old_a1 = a1; 
	double old_a2 = a2;
	double turns_a1 = floor (old_a1 / CH_C_2PI);
	double turns_a2 = floor (old_a2 / CH_C_2PI);
	double a1U = turns_a1 * CH_C_2PI + periodic_a1 + CH_C_2PI;
	double a1M = turns_a1 * CH_C_2PI + periodic_a1;
	double a1L = turns_a1 * CH_C_2PI + periodic_a1 - CH_C_2PI;
	a1 = a1M;
	if (fabs(a1U - old_a1) < fabs(a1M - old_a1))
		a1 = a1U;
	if (fabs(a1L - a1) < fabs(a1M - a1))
		a1 = a1L;
	double a2U = turns_a2 * CH_C_2PI + periodic_a2 + CH_C_2PI;
	double a2M = turns_a2 * CH_C_2PI + periodic_a2;
	double a2L = turns_a2 * CH_C_2PI + periodic_a2 - CH_C_2PI;
	a2 = a2M;
	if (fabs(a2U - old_a2) < fabs(a2M - old_a2))
		a2 = a2U;
	if (fabs(a2L - a2) < fabs(a2M - a2))
		a2 = a2L;

	     // correct marker positions if phasing is not correct
	double m_delta =0;
    if (this->checkphase)
    {
		double realtau = tau; 
		//if (this->epicyclic) 
		//	realtau = -tau;
        
        m_delta = a1 - phase - (a2/realtau);

        if (m_delta> CH_C_PI) m_delta -= (CH_C_2PI);		 // range -180..+180 is better than 0...360
        if (m_delta> (CH_C_PI/4.0)) m_delta = (CH_C_PI/4.0); // phase correction only in +/- 45°
        if (m_delta<-(CH_C_PI/4.0)) m_delta =-(CH_C_PI/4.0);
		//***TODO***
    }


    // Move markers 1 and 2 to align them as pulley ends

	ChVector<> d21_w = dcc_w - Get_shaft_dir1()* Vdot (Get_shaft_dir1(), dcc_w);
	ChVector<> D21_w = Vnorm(d21_w);

	this->shaft_dist = d21_w.Length();
	
	ChVector<> U1_w = Vcross(Get_shaft_dir1(), D21_w);

	double gamma1 = acos( (r1-r2) / shaft_dist);

	ChVector<> Ru_w =  D21_w*cos(gamma1) + U1_w*sin(gamma1);
	ChVector<> Rl_w =  D21_w*cos(gamma1) - U1_w*sin(gamma1);

	this->belt_up1  = Get_shaft_pos1()+ Ru_w*r1;
	this->belt_low1 = Get_shaft_pos1()+ Rl_w*r1;
	this->belt_up2  = Get_shaft_pos1()+ d21_w + Ru_w*r2;
	this->belt_low2 = Get_shaft_pos1()+ d21_w + Rl_w*r2;

		// marker alignment
	ChMatrix33<> maU;
	ChMatrix33<> maL;

	ChVector<> Dxu = Vnorm(belt_up2 - belt_up1);
	ChVector<> Dyu = Ru_w;
	ChVector<> Dzu = Vnorm (Vcross(Dxu, Dyu));
	Dyu = Vnorm (Vcross(Dzu, Dxu));
	maU.Set_A_axis(Dxu,Dyu,Dzu);

            // ! Require that the BDF routine of marker won't handle speed and acc.calculus of the moved marker 2!
    marker2->SetMotionType(ChMarker::M_MOTION_EXTERNAL);
    marker1->SetMotionType(ChMarker::M_MOTION_EXTERNAL);

	ChCoordsys<> newmarkpos;

        // move marker1 in proper positions
    newmarkpos.pos = this->belt_up1;
    newmarkpos.rot = maU.Get_A_quaternion();
    marker1->Impose_Abs_Coord(newmarkpos);        //move marker1 into teeth position
        // move marker2 in proper positions
    newmarkpos.pos = this->belt_up2;
    newmarkpos.rot = maU.Get_A_quaternion();
    marker2->Impose_Abs_Coord(newmarkpos);        //move marker2 into teeth position

	double phase_correction_up = m_delta*r1;
	double phase_correction_low = - phase_correction_up;
	double hU = Vlenght(belt_up2- belt_up1)  + phase_correction_up;
	double hL = Vlenght(belt_low2- belt_low1) + phase_correction_low;

        // imposed relative positions/speeds
    deltaC.pos = ChVector<>(-hU, 0, 0);
    deltaC_dt.pos = VNULL;
    deltaC_dtdt.pos = VNULL;

    deltaC.rot = QUNIT;             // no relative rotations imposed!
    deltaC_dt.rot = QNULL;
    deltaC_dtdt.rot = QNULL;
}
Exemple #6
0
// -----------------------------------------------------------------------------
// -----------------------------------------------------------------------------
void ChPitmanArm::Initialize(std::shared_ptr<ChBodyAuxRef> chassis,
                             const ChVector<>& location,
                             const ChQuaternion<>& rotation) {
    m_position = ChCoordsys<>(location, rotation);

    // Chassis orientation (expressed in absolute frame)
    // Recall that the suspension reference frame is aligned with the chassis.
    ChQuaternion<> chassisRot = chassis->GetFrame_REF_to_abs().GetRot();

    // Express the steering reference frame in the absolute coordinate system.
    ChFrame<> steering_to_abs(location, rotation);
    steering_to_abs.ConcatenatePreTransformation(chassis->GetFrame_REF_to_abs());

    // Transform all points and directions to absolute frame.
    std::vector<ChVector<>> points(NUM_POINTS);
    std::vector<ChVector<>> dirs(NUM_DIRS);

    for (int i = 0; i < NUM_POINTS; i++) {
        ChVector<> rel_pos = getLocation(static_cast<PointId>(i));
        points[i] = steering_to_abs.TransformPointLocalToParent(rel_pos);
    }

    for (int i = 0; i < NUM_DIRS; i++) {
        ChVector<> rel_dir = getDirection(static_cast<DirectionId>(i));
        dirs[i] = steering_to_abs.TransformDirectionLocalToParent(rel_dir);
    }

    // Unit vectors for orientation matrices.
    ChVector<> u;
    ChVector<> v;
    ChVector<> w;
    ChMatrix33<> rot;

    // Create and initialize the steering link body
    m_link = std::shared_ptr<ChBody>(chassis->GetSystem()->NewBody());
    m_link->SetNameString(m_name + "_link");
    m_link->SetPos(points[STEERINGLINK]);
    m_link->SetRot(steering_to_abs.GetRot());
    m_link->SetMass(getSteeringLinkMass());
    if (m_vehicle_frame_inertia) {
        ChMatrix33<> inertia = TransformInertiaMatrix(getSteeringLinkInertiaMoments(), getSteeringLinkInertiaProducts(),
                                                      chassisRot, steering_to_abs.GetRot());
        m_link->SetInertia(inertia);
    } else {
        m_link->SetInertiaXX(getSteeringLinkInertiaMoments());
        m_link->SetInertiaXY(getSteeringLinkInertiaProducts());
    }
    chassis->GetSystem()->AddBody(m_link);

    m_pP = m_link->TransformPointParentToLocal(points[UNIV]);
    m_pI = m_link->TransformPointParentToLocal(points[REVSPH_S]);
    m_pTP = m_link->TransformPointParentToLocal(points[TIEROD_PA]);
    m_pTI = m_link->TransformPointParentToLocal(points[TIEROD_IA]);

    // Create and initialize the Pitman arm body
    m_arm = std::shared_ptr<ChBody>(chassis->GetSystem()->NewBody());
    m_arm->SetNameString(m_name + "_arm");
    m_arm->SetPos(points[PITMANARM]);
    m_arm->SetRot(steering_to_abs.GetRot());
    m_arm->SetMass(getPitmanArmMass());
    if (m_vehicle_frame_inertia) {
        ChMatrix33<> inertia = TransformInertiaMatrix(getPitmanArmInertiaMoments(), getPitmanArmInertiaProducts(),
                                                      chassisRot, steering_to_abs.GetRot());
        m_arm->SetInertia(inertia);
    } else {
        m_arm->SetInertiaXX(getPitmanArmInertiaMoments());
        m_arm->SetInertiaXY(getPitmanArmInertiaProducts());
    }
    chassis->GetSystem()->AddBody(m_arm);

    // Cache points for arm visualization (expressed in the arm frame)
    m_pC = m_arm->TransformPointParentToLocal(points[REV]);
    m_pL = m_arm->TransformPointParentToLocal(points[UNIV]);

    // Create and initialize the revolute joint between chassis and Pitman arm.
    // Note that this is modeled as a ChLinkEngine to allow driving it with
    // imposed rotation (steering input).
    // The z direction of the joint orientation matrix is dirs[REV_AXIS], assumed
    // to be a unit vector.
    u = points[PITMANARM] - points[REV];
    v = Vcross(dirs[REV_AXIS], u);
    v.Normalize();
    u = Vcross(v, dirs[REV_AXIS]);
    rot.Set_A_axis(u, v, dirs[REV_AXIS]);

    m_revolute = std::make_shared<ChLinkMotorRotationAngle>();
    m_revolute->SetNameString(m_name + "_revolute");
    m_revolute->Initialize(chassis, m_arm, ChFrame<>(points[REV], rot.Get_A_quaternion()));
    auto motor_fun = std::make_shared<ChFunction_Setpoint>();
    m_revolute->SetAngleFunction(motor_fun);
    chassis->GetSystem()->AddLink(m_revolute);

    // Create and initialize the universal joint between the Pitman arm and steering link.
    // The x and y directions of the joint orientation matrix are given by
    // dirs[UNIV_AXIS_ARM] and dirs[UNIV_AXIS_LINK], assumed to be unit vectors
    // and orthogonal.
    w = Vcross(dirs[UNIV_AXIS_ARM], dirs[UNIV_AXIS_LINK]);
    rot.Set_A_axis(dirs[UNIV_AXIS_ARM], dirs[UNIV_AXIS_LINK], w);

    m_universal = std::make_shared<ChLinkUniversal>();
    m_universal->SetNameString(m_name + "_universal");
    m_universal->Initialize(m_arm, m_link, ChFrame<>(points[UNIV], rot.Get_A_quaternion()));
    chassis->GetSystem()->AddLink(m_universal);

    // Create and initialize the revolute-spherical joint (massless idler arm).
    // The length of the idler arm is the distance between the two hardpoints.
    // The z direction of the revolute joint orientation matrix is
    // dirs[REVSPH_AXIS], assumed to be a unit vector.
    double distance = (points[REVSPH_S] - points[REVSPH_R]).Length();

    u = points[REVSPH_S] - points[REVSPH_R];
    v = Vcross(dirs[REVSPH_AXIS], u);
    v.Normalize();
    u = Vcross(v, dirs[REVSPH_AXIS]);
    rot.Set_A_axis(u, v, dirs[REVSPH_AXIS]);

    m_revsph = std::make_shared<ChLinkRevoluteSpherical>();
    m_revsph->SetNameString(m_name + "_revsph");
    m_revsph->Initialize(chassis, m_link, ChCoordsys<>(points[REVSPH_R], rot.Get_A_quaternion()), distance);
    chassis->GetSystem()->AddLink(m_revsph);
}