Velocity Controllers

This package provides a collection of velocity controllers, which calculate control commands (e.g., a wrench) needed to track a velocity reference signal.

Integral Sliding Mode Controller

A chainable dynamic controller designed by Palmer et al. ¹ that provides robustness to matched uncertainties and attenuates chatter.

Plugin Library

velocity_controllers/integral_sliding_mode_controller

References

• Target velocity V_ref: v_xref, v_yref, v_zref, w_rxref, w_ryref, w_rzref [m/s and rad/s]

State Feedback

• Measured velocity V: v_x, v_y, v_z, w_rx, w_ry, w_rz [m/s and rad/s]
• Vehicle orientation measured with respect to the inertial frame Q: q_x, q_y, q_z, q_w

Commands

The output of this controller is a wrench with force components F_x, F_y, F_z and torque components T_rx, T_ry, T_rz in N and Nm, respectively.

Subscribers

• integral_sliding_mode_controller/reference [geometry_msgs::msg::Twist]
• integral_sliding_mode_controller/system_state [geometry_msgs::msg::Twist]

Publishers

• integral_sliding_mode_controller/status [control_msgs::msg::MultiDOFStateStamped]

Parameters

• use_external_measured_states: Flag to use velocity measurements obtained from a topic instead of from state interfaces. [bool]
• enable_parameter_update_without_reactivation: If enabled, the parameters will be dynamically updated while the controller is running. [bool]
• reference_controller: The prefix of the reference controller to send command to. This can be used to configure command interfaces in chained mode. [string]
• tf:
  • base_frame: The name of the vehicle base frame. [string]
  • odom_frame: The name of the inertial frame. [string]
• gains:
  • rho: The sliding mode gain. This adjusts how quickly the controller drives the system to the sliding surface. [double]
  • lambda: The boundary thickness of the tanh function used to attenuate ISMC chatter. [double]
  • Kp: The proportional gains for the controller provided in the order: x, y, z, rx, ry, rz. [double array]
• hydrodynamics:
  • mass: The mass of the vehicle. [double]
  • moments_of_inertia: The moments of inertia of the vehicle in the order: I_xx, I_yy, I_zz. [double array]
  • added_mass: The added mass coefficients of the vehicle in the order: X_du, Y_dv, Z_dw, K_dp, M_dq, N_dr. [double array]
  • weight: The weight of the vehicle. [double]
  • buoyancy: The buoyancy of the vehicle [double]
  • center_of_buoyancy: The center-of-buoyancy of the vehicle in the order: x, y, z. [double array]
  • center_of_gravity: The center-of-gravity of the vehicle in the order: x, y, z. [double array]
  • linear_damping: The linear damping coefficients of the vehicle in the order: X_u, Y_v, Z_w, K_p, M_q, N_r. [double array]
  • quadratic_damping: The quadratic damping coefficients of the vehicle in the order: X_uu, Y_vv, Z_ww, K_pp, M_qq, N_rr. [double array]

Footnotes

1. E. Palmer, C. Holm, and G. Hollinger, "Angler: An Autonomy Framework for Intervention Tasks with Lightweight Underwater Vehicle Manipulator Systems," in IEEE International Conference on Robotics and Automation (ICRA), 2024. ↩