CM_DOG/User/component/unitreeLeg.cpp

/**********************************************************************
 Copyright (c) 2020-2023, Unitree Robotics.Co.Ltd. All rights reserved.
***********************************************************************/
#include "common/unitreeLeg.h"
#include <iostream>


/************************/
/*******QuadrupedLeg*****/
/************************/
QuadrupedLeg::QuadrupedLeg(int legID, float abadLinkLength, float hipLinkLength, 
                           float kneeLinkLength, Vec3 pHip2B)
            :_abadLinkLength(abadLinkLength), 
             _hipLinkLength(hipLinkLength), 
             _kneeLinkLength(kneeLinkLength), 
             _pHip2B(pHip2B){
    if (legID == 0 || legID == 2)
        _sideSign = -1;
    else if (legID == 1 || legID == 3)
        _sideSign = 1;
    else{
        std::cout << "Leg ID incorrect!" << std::endl;
        exit(-1);
    }
}

// Forward Kinematics
Vec3 QuadrupedLeg::calcPEe2H(Vec3 q){
    float l1 = _sideSign * _abadLinkLength;
    float l2 = -_hipLinkLength;
    float l3 = -_kneeLinkLength;

    float s1 = std::sin(q(0));
    float s2 = std::sin(q(1));
    float s3 = std::sin(q(2));

    float c1 = std::cos(q(0));
    float c2 = std::cos(q(1));
    float c3 = std::cos(q(2));

    float c23 = c2 * c3 - s2 * s3;
    float s23 = s2 * c3 + c2 * s3;

    Vec3 pEe2H;

    pEe2H(0) = l3 * s23 + l2 * s2;
    pEe2H(1) = -l3 * s1 * c23 + l1 * c1 - l2 * c2 * s1;
    pEe2H(2) =  l3 * c1 * c23 + l1 * s1 + l2 * c1 * c2;

    return pEe2H;
}

// Forward Kinematics
Vec3 QuadrupedLeg::calcPEe2B(Vec3 q){
    return _pHip2B + calcPEe2H(q);
}

// Derivative Forward Kinematics
Vec3 QuadrupedLeg::calcVEe(Vec3 q, Vec3 qd){
    return calcJaco(q) * qd;
}

// Inverse Kinematics
Vec3 QuadrupedLeg::calcQ(Vec3 pEe, FrameType frame){
    Vec3 pEe2H;
    if(frame == FrameType::HIP)
        pEe2H = pEe;
    else if(frame == FrameType::BODY)
        pEe2H = pEe - _pHip2B;
    else{
        std::cout << "[ERROR] The frame of QuadrupedLeg::calcQ can only be HIP or BODY!" << std::endl;
        exit(-1);
    }

    float q1, q2, q3;
    Vec3 qResult;
    float px, py, pz;
    float b2y, b3z, b4z, a, b, c;

    px = pEe2H(0);
    py = pEe2H(1);
    pz = pEe2H(2);

    b2y = _abadLinkLength * _sideSign;
    b3z = -_hipLinkLength;
    b4z = -_kneeLinkLength;
    a = _abadLinkLength;
    c = sqrt(pow(px, 2) + pow(py, 2) + pow(pz, 2)); // whole length
    b = sqrt(pow(c, 2) - pow(a, 2)); // distance between shoulder and footpoint

    q1 = q1_ik(py, pz, b2y);
    q3 = q3_ik(b3z, b4z, b);
    q2 = q2_ik(q1, q3, px, py, pz, b3z, b4z);

    qResult(0) = q1;
    qResult(1) = q2;
    qResult(2) = q3;

    return qResult;
}

// Derivative Inverse Kinematics
Vec3 QuadrupedLeg::calcQd(Vec3 q, Vec3 vEe){
    return calcJaco(q).inverse() * vEe;
}

// Derivative Inverse Kinematics
Vec3 QuadrupedLeg::calcQd(Vec3 pEe, Vec3 vEe, FrameType frame){
    Vec3 q = calcQ(pEe, frame);
    return calcJaco(q).inverse() * vEe;
}

// Inverse Dynamics
Vec3 QuadrupedLeg::calcTau(Vec3 q, Vec3 force){
    return calcJaco(q).transpose() * force;
}

// Jacobian Matrix
Mat3 QuadrupedLeg::calcJaco(Vec3 q){
    Mat3 jaco;

    float l1 = _abadLinkLength * _sideSign;
    float l2 = -_hipLinkLength;
    float l3 = -_kneeLinkLength;

    float s1 = std::sin(q(0));
    float s2 = std::sin(q(1));
    float s3 = std::sin(q(2));

    float c1 = std::cos(q(0));
    float c2 = std::cos(q(1));
    float c3 = std::cos(q(2));

    float c23 = c2 * c3 - s2 * s3;
    float s23 = s2 * c3 + c2 * s3;
    jaco(0, 0) = 0;
    jaco(1, 0) = -l3 * c1 * c23 - l2 * c1 * c2 - l1 * s1;
    jaco(2, 0) = -l3 * s1 * c23 - l2 * c2 * s1 + l1 * c1;
    jaco(0, 1) = l3 * c23 + l2 * c2;
    jaco(1, 1) = l3 * s1 * s23 + l2 * s1 * s2;
    jaco(2, 1) = -l3 * c1 * s23 - l2 * c1 * s2;
    jaco(0, 2) = l3 * c23;
    jaco(1, 2) = l3 * s1 * s23;
    jaco(2, 2) = -l3 * c1 * s23;

    return jaco;
}

float QuadrupedLeg::q1_ik(float py, float pz, float l1){
    float q1;
    float L = sqrt(pow(py,2)+pow(pz,2)-pow(l1,2));
    q1 = atan2(pz*l1+py*L, py*l1-pz*L);
    return q1;
}

float QuadrupedLeg::q3_ik(float b3z, float b4z, float b){
    float q3, temp;
    temp = (pow(b3z, 2) + pow(b4z, 2) - pow(b, 2))/(2*fabs(b3z*b4z));
    if(temp>1) temp = 1;
    if(temp<-1) temp = -1;
    q3 = acos(temp);
    q3 = -(M_PI - q3); //0~180
    return q3;
}

float QuadrupedLeg::q2_ik(float q1, float q3, float px, float py, float pz, float b3z, float b4z){
    float q2, a1, a2, m1, m2;
    
    a1 = py*sin(q1) - pz*cos(q1);
    a2 = px;
    m1 = b4z*sin(q3);
    m2 = b3z + b4z*cos(q3);
    q2 = atan2(m1*a1+m2*a2, m1*a2-m2*a1);
    return q2;
}