#ifndef MULTIBODYTREE_HPP_ #define MULTIBODYTREE_HPP_ #include "IDConfig.hpp" #include "IDMath.hpp" namespace btInverseDynamics { /// Enumeration of supported joint types enum JointType { /// no degree of freedom, moves with parent FIXED = 0, /// one rotational degree of freedom relative to parent REVOLUTE, /// one translational degree of freedom relative to parent PRISMATIC, /// six degrees of freedom relative to parent FLOATING, /// three degrees of freedom, relative to parent SPHERICAL }; /// Interface class for calculating inverse dynamics for tree structured /// multibody systems /// /// Note on degrees of freedom /// The q vector contains the generalized coordinate set defining the tree's configuration. /// Every joint adds elements that define the corresponding link's frame pose relative to /// its parent. For the joint types that is: /// - FIXED: none /// - REVOLUTE: angle of rotation [rad] /// - PRISMATIC: displacement [m] /// - FLOATING: Euler x-y-z angles [rad] and displacement in body-fixed frame of parent [m] /// (in that order) /// - SPHERICAL: Euler x-y-z angles [rad] /// The u vector contains the generalized speeds, which are /// - FIXED: none /// - REVOLUTE: time derivative of angle of rotation [rad/s] /// - PRISMATIC: time derivative of displacement [m/s] /// - FLOATING: angular velocity [rad/s] (*not* time derivative of rpy angles) /// and time derivative of displacement in parent frame [m/s] // - SPHERICAL: angular velocity [rad/s] /// /// The q and u vectors are obtained by stacking contributions of all bodies in one /// vector in the order of body indices. /// /// Note on generalized forces: analogous to u, i.e., /// - FIXED: none /// - REVOLUTE: moment [Nm], about joint axis /// - PRISMATIC: force [N], along joint axis /// - FLOATING: moment vector [Nm] and force vector [N], both in body-fixed frame /// (in that order) /// - SPHERICAL: moment vector [Nm] /// TODO - force element interface (friction, springs, dampers, etc) /// - gears and motor inertia class MultiBodyTree { public: ID_DECLARE_ALIGNED_ALLOCATOR(); /// The contructor. /// Initialization & allocation is via addBody and buildSystem calls. MultiBodyTree(); /// the destructor. This also deallocates all memory ~MultiBodyTree(); /// Add body to the system. this allocates memory and not real-time safe. /// This only adds the data to an initial cache. After all bodies have been /// added, /// the system is setup using the buildSystem call /// @param body_index index of the body to be added. Must >=0, <number of bodies, /// and index of parent must be < index of body /// @param parent_index index of the parent body /// The root of the tree has index 0 and its parent (the world frame) /// is assigned index -1 /// the rotation and translation relative to the parent are taken as /// pose of the root body relative to the world frame. Other parameters /// are ignored /// @param JointType type of joint connecting the body to the parent /// @param mass the mass of the body /// @param body_r_body_com the center of mass of the body relative to and /// described in /// the body fixed frame, which is located in the joint axis connecting /// the body to its parent /// @param body_I_body the moment of inertia of the body w.r.t the body-fixed /// frame /// (ie, the reference point is the origin of the body-fixed frame and /// the matrix is written /// w.r.t. those unit vectors) /// @param parent_r_parent_body_ref position of joint relative to the parent /// body's reference frame /// for q=0, written in the parent bodies reference frame /// @param body_axis_of_motion translation/rotation axis in body-fixed frame. /// Ignored for joints that are not revolute or prismatic. /// must be a unit vector. /// @param body_T_parent_ref transform matrix from parent to body reference /// frame for q=0. /// This is the matrix transforming a vector represented in the /// parent's reference frame into one represented /// in this body's reference frame. /// ie, if parent_vec is a vector in R^3 whose components are w.r.t to /// the parent's reference frame, /// then the same vector written w.r.t. this body's frame (for q=0) is /// given by /// body_vec = parent_R_body_ref * parent_vec /// @param user_ptr pointer to user data /// @param user_int pointer to user integer /// @return 0 on success, -1 on error int addBody(int body_index, int parent_index, JointType joint_type, const vec3& parent_r_parent_body_ref, const mat33& body_T_parent_ref, const vec3& body_axis_of_motion, idScalar mass, const vec3& body_r_body_com, const mat33& body_I_body, const int user_int, void* user_ptr); /// set policy for invalid mass properties /// @param flag if true, invalid mass properties are accepted, /// the default is false void setAcceptInvalidMassParameters(bool flag); /// @return the mass properties policy flag bool getAcceptInvalidMassProperties() const; /// build internal data structures /// call this after all bodies have been added via addBody /// @return 0 on success, -1 on error int finalize(); /// pretty print ascii description of tree to stdout void printTree(); /// print tree data to stdout void printTreeData(); /// Calculate joint forces for given generalized state & derivatives. /// This also updates kinematic terms computed in calculateKinematics. /// If gravity is not set to zero, acceleration terms will contain /// gravitational acceleration. /// @param q generalized coordinates /// @param u generalized velocities. In the general case, u=T(q)*dot(q) and dim(q)>=dim(u) /// @param dot_u time derivative of u /// @param joint_forces this is where the resulting joint forces will be /// stored. dim(joint_forces) = dim(u) /// @return 0 on success, -1 on error int calculateInverseDynamics(const vecx& q, const vecx& u, const vecx& dot_u, vecx* joint_forces); /// Calculate joint space mass matrix /// @param q generalized coordinates /// @param initialize_matrix if true, initialize mass matrix with zero. /// If mass_matrix is initialized to zero externally and only used /// for mass matrix computations for the same system, it is safe to /// set this to false. /// @param set_lower_triangular_matrix if true, the lower triangular section of mass_matrix /// is also populated, otherwise not. /// @param mass_matrix matrix for storing the output (should be dim(q)xdim(q)) /// @return -1 on error, 0 on success int calculateMassMatrix(const vecx& q, const bool update_kinematics, const bool initialize_matrix, const bool set_lower_triangular_matrix, matxx* mass_matrix); /// Calculate joint space mass matrix. /// This version will update kinematics, initialize all mass_matrix elements to zero and /// populate all mass matrix entries. /// @param q generalized coordinates /// @param mass_matrix matrix for storing the output (should be dim(q)xdim(q)) /// @return -1 on error, 0 on success int calculateMassMatrix(const vecx& q, matxx* mass_matrix); /// Calculates kinematics also calculated in calculateInverseDynamics, /// but not dynamics. /// This function ensures that correct accelerations are computed that do not /// contain gravitational acceleration terms. /// Does not calculate Jacobians, but only vector quantities (positions, velocities & accelerations) int calculateKinematics(const vecx& q, const vecx& u, const vecx& dot_u); /// Calculate position kinematics int calculatePositionKinematics(const vecx& q); /// Calculate position and velocity kinematics int calculatePositionAndVelocityKinematics(const vecx& q, const vecx& u); #if (defined BT_ID_HAVE_MAT3X) && (defined BT_ID_WITH_JACOBIANS) /// Calculate Jacobians (dvel/du), as well as velocity-dependent accelearation components /// d(Jacobian)/dt*u /// This function assumes that calculateInverseDynamics was called, or calculateKinematics, /// or calculatePositionAndVelocityKinematics int calculateJacobians(const vecx& q, const vecx& u); /// Calculate Jacobians (dvel/du) /// This function assumes that calculateInverseDynamics was called, or /// one of the calculateKineamtics functions int calculateJacobians(const vecx& q); #endif // BT_ID_HAVE_MAT3X /// set gravitational acceleration /// the default is [0;0;-9.8] in the world frame /// @param gravity the gravitational acceleration in world frame /// @return 0 on success, -1 on error int setGravityInWorldFrame(const vec3& gravity); /// returns number of bodies in tree int numBodies() const; /// returns number of mechanical degrees of freedom (dimension of q-vector) int numDoFs() const; /// get origin of a body-fixed frame, represented in world frame /// @param body_index index for frame/body /// @param world_origin pointer for return data /// @return 0 on success, -1 on error int getBodyOrigin(const int body_index, vec3* world_origin) const; /// get center of mass of a body, represented in world frame /// @param body_index index for frame/body /// @param world_com pointer for return data /// @return 0 on success, -1 on error int getBodyCoM(const int body_index, vec3* world_com) const; /// get transform from of a body-fixed frame to the world frame /// @param body_index index for frame/body /// @param world_T_body pointer for return data /// @return 0 on success, -1 on error int getBodyTransform(const int body_index, mat33* world_T_body) const; /// get absolute angular velocity for a body, represented in the world frame /// @param body_index index for frame/body /// @param world_omega pointer for return data /// @return 0 on success, -1 on error int getBodyAngularVelocity(const int body_index, vec3* world_omega) const; /// get linear velocity of a body, represented in world frame /// @param body_index index for frame/body /// @param world_velocity pointer for return data /// @return 0 on success, -1 on error int getBodyLinearVelocity(const int body_index, vec3* world_velocity) const; /// get linear velocity of a body's CoM, represented in world frame /// (not required for inverse dynamics, provided for convenience) /// @param body_index index for frame/body /// @param world_vel_com pointer for return data /// @return 0 on success, -1 on error int getBodyLinearVelocityCoM(const int body_index, vec3* world_velocity) const; /// get origin of a body-fixed frame, represented in world frame /// @param body_index index for frame/body /// @param world_origin pointer for return data /// @return 0 on success, -1 on error int getBodyAngularAcceleration(const int body_index, vec3* world_dot_omega) const; /// get origin of a body-fixed frame, represented in world frame /// NOTE: this will include the gravitational acceleration, so the actual acceleration is /// obtainened by setting gravitational acceleration to zero, or subtracting it. /// @param body_index index for frame/body /// @param world_origin pointer for return data /// @return 0 on success, -1 on error int getBodyLinearAcceleration(const int body_index, vec3* world_acceleration) const; #if (defined BT_ID_HAVE_MAT3X) && (defined BT_ID_WITH_JACOBIANS) // get translational jacobian, in world frame (dworld_velocity/du) int getBodyJacobianTrans(const int body_index, mat3x* world_jac_trans) const; // get rotational jacobian, in world frame (dworld_omega/du) int getBodyJacobianRot(const int body_index, mat3x* world_jac_rot) const; // get product of translational jacobian derivative * generatlized velocities int getBodyDotJacobianTransU(const int body_index, vec3* world_dot_jac_trans_u) const; // get product of rotational jacobian derivative * generatlized velocities int getBodyDotJacobianRotU(const int body_index, vec3* world_dot_jac_rot_u) const; #endif // BT_ID_HAVE_MAT3X /// returns the (internal) index of body /// @param body_index is the index of a body /// @param parent_index pointer to where parent index will be stored /// @return 0 on success, -1 on error int getParentIndex(const int body_index, int* parent_index) const; /// get joint type /// @param body_index index of the body /// @param joint_type the corresponding joint type /// @return 0 on success, -1 on failure int getJointType(const int body_index, JointType* joint_type) const; /// get joint type as string /// @param body_index index of the body /// @param joint_type string naming the corresponding joint type /// @return 0 on success, -1 on failure int getJointTypeStr(const int body_index, const char** joint_type) const; /// get offset translation to parent body (see addBody) /// @param body_index index of the body /// @param r the offset translation (see above) /// @return 0 on success, -1 on failure int getParentRParentBodyRef(const int body_index, vec3* r) const; /// get offset rotation to parent body (see addBody) /// @param body_index index of the body /// @param T the transform (see above) /// @return 0 on success, -1 on failure int getBodyTParentRef(const int body_index, mat33* T) const; /// get axis of motion (see addBody) /// @param body_index index of the body /// @param axis the axis (see above) /// @return 0 on success, -1 on failure int getBodyAxisOfMotion(const int body_index, vec3* axis) const; /// get offset for degrees of freedom of this body into the q-vector /// @param body_index index of the body /// @param q_offset offset the q vector /// @return -1 on error, 0 on success int getDoFOffset(const int body_index, int* q_offset) const; /// get user integer. not used by the library. /// @param body_index index of the body /// @param user_int the user integer /// @return 0 on success, -1 on error int getUserInt(const int body_index, int* user_int) const; /// get user pointer. not used by the library. /// @param body_index index of the body /// @param user_ptr the user pointer /// @return 0 on success, -1 on error int getUserPtr(const int body_index, void** user_ptr) const; /// set user integer. not used by the library. /// @param body_index index of the body /// @param user_int the user integer /// @return 0 on success, -1 on error int setUserInt(const int body_index, const int user_int); /// set user pointer. not used by the library. /// @param body_index index of the body /// @param user_ptr the user pointer /// @return 0 on success, -1 on error int setUserPtr(const int body_index, void* const user_ptr); /// set mass for a body /// @param body_index index of the body /// @param mass the mass to set /// @return 0 on success, -1 on failure int setBodyMass(const int body_index, const idScalar mass); /// set first moment of mass for a body /// (mass * center of mass, in body fixed frame, relative to joint) /// @param body_index index of the body /// @param first_mass_moment the vector to set /// @return 0 on success, -1 on failure int setBodyFirstMassMoment(const int body_index, const vec3& first_mass_moment); /// set second moment of mass for a body /// (moment of inertia, in body fixed frame, relative to joint) /// @param body_index index of the body /// @param second_mass_moment the inertia matrix /// @return 0 on success, -1 on failure int setBodySecondMassMoment(const int body_index, const mat33& second_mass_moment); /// get mass for a body /// @param body_index index of the body /// @param mass the mass /// @return 0 on success, -1 on failure int getBodyMass(const int body_index, idScalar* mass) const; /// get first moment of mass for a body /// (mass * center of mass, in body fixed frame, relative to joint) /// @param body_index index of the body /// @param first_moment the vector /// @return 0 on success, -1 on failure int getBodyFirstMassMoment(const int body_index, vec3* first_mass_moment) const; /// get second moment of mass for a body /// (moment of inertia, in body fixed frame, relative to joint) /// @param body_index index of the body /// @param second_mass_moment the inertia matrix /// @return 0 on success, -1 on failure int getBodySecondMassMoment(const int body_index, mat33* second_mass_moment) const; /// set all user forces and moments to zero void clearAllUserForcesAndMoments(); /// Add an external force to a body, acting at the origin of the body-fixed frame. /// Calls to addUserForce are cumulative. Set the user force and moment to zero /// via clearAllUserForcesAndMoments() /// @param body_force the force represented in the body-fixed frame of reference /// @return 0 on success, -1 on error int addUserForce(const int body_index, const vec3& body_force); /// Add an external moment to a body. /// Calls to addUserMoment are cumulative. Set the user force and moment to zero /// via clearAllUserForcesAndMoments() /// @param body_moment the moment represented in the body-fixed frame of reference /// @return 0 on success, -1 on error int addUserMoment(const int body_index, const vec3& body_moment); private: // flag indicating if system has been initialized bool m_is_finalized; // flag indicating if mass properties are physically valid bool m_mass_parameters_are_valid; // flag defining if unphysical mass parameters are accepted bool m_accept_invalid_mass_parameters; // This struct implements the inverse dynamics calculations class MultiBodyImpl; MultiBodyImpl* m_impl; // cache data structure for initialization class InitCache; InitCache* m_init_cache; }; } // namespace btInverseDynamics #endif // MULTIBODYTREE_HPP_