SRSSolver

SRSSolver#

SRSSolver provides analytical IK for 7-DOF arms with a spherical-rotational-spherical (S-R-S) joint structure, including joint limits and multiple-solution sampling.

S-R-S describes three intersecting shoulder axes, one elbow axis, and three intersecting wrist axes. The extra degree of freedom permits multiple joint configurations for the same end-effector pose.

Configuration#

SRSSolver is configured via the SRSSolverCfg class, allowing detailed control over kinematic parameters and solver behavior.

from embodichain.data import get_data_path
from embodichain_robots.dexforce.w1.types import (
    DexforceW1ArmSide,
    DexforceW1Version,
)
from embodichain_robots.dexforce.w1.params import (
    W1ArmKineParams,
)
from embodichain.lab.sim.motion.solvers.srs_solver import SRSSolver, SRSSolverCfg

arm_params = W1ArmKineParams(
    arm_side=DexforceW1ArmSide.RIGHT,
    version=DexforceW1Version.V021,
)

cfg = SRSSolverCfg(
    urdf_path=get_data_path("DexforceW1V021/DexforceW1_v02_1.urdf"),
    joint_names=[f"RIGHT_J{i+1}" for i in range(7)],
    end_link_name="right_ee",
    root_link_name="right_arm_base",
    dh_params=arm_params.dh_params,
    user_qpos_limits=arm_params.qpos_limits,
    T_e_oe=arm_params.T_e_oe,
    T_b_ob=arm_params.T_b_ob,
    link_lengths=arm_params.link_lengths,
    rotation_directions=arm_params.rotation_directions,
)

solver = SRSSolver(cfg, num_envs=1, device="cuda")

Solver-specific behavior#

See shared FK/IK conventions for the common call pattern and return order.

The default get_ik() result contains success flags (B,) and a selected solution (B, 1, 7). return_all_solutions=True retains multiple solutions. Configure arm-angle sampling and joint limits for the desired redundancy resolution; the robot must match the S-R-S geometry.

References#

  • Analytical Inverse Kinematic Computation for 7-DOF Redundant Manipulators With Joint Limits and Its Application to Redundancy Resolution
    Masayuki Shimizu, Hiromu Kakuya, Woo-Keun Yoon, Kosei Kitagaki, Kazuhiro Kosuge
    IEEE Transactions on Robotics, 2008
    DOI: 10.1109/TRO.2008.2003266
    This paper presents an analytical approach for solving the inverse kinematics of 7-DOF redundant manipulators, including joint limit handling and redundancy resolution strategies.

  • Position-based kinematics for 7-DoF serial manipulators with global configuration control, joint limit, and singularity avoidance
    Carlos Faria, Flora Ferreira, Wolfram Erlhagen, Sérgio Monteiro, Estela Bicho
    Mechanism and Machine Theory, 2018
    DOI: 10.1016/j.mechmachtheory.2017.10.025
    This work introduces position-based kinematic algorithms for 7-DOF manipulators, focusing on global configuration control, joint limit enforcement, and singularity avoidance.

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