How to Send Joint Velocity Commands to Kinova Gen3 in Simulink Using KORTEX SDK?

Hello,

I am currently working on implementing a closed-loop IBVS (Image-Based Visual Servoing) control for a Kinova Gen3 robotic arm in Simulink. I calculate joint velocities using a PID-based visual servo control law and would like to send these velocities directly to the robot.

I am following the example from the Connect to Kinova Gen3 from Simulink demo (link: (https://www.mathworks.com/help/robotics/robotmanipulator/ug/connect-gen3-simulink.html), which uses two System objects: 1. TrajectoryFeeder 2. KORTEX Main (provided via kortex.m from Kinova's SDK)

From what I understand, the kortex.m interface currently supports: 1. SendJointAngles 2. SendPreComputedTrajectory

However, it does not include a method like SendJointSpeeds() to send joint velocities directly.

My Questions: 1. Should I extend kortex.m to add a method like the following to send joint velocities?

function [isOk] = SendJointSpeeds(obj, joint_vel_cmd) if coder.target('MATLAB') [result] = kortexApiMexInterface('SendJointSpeeds', obj.apiHandle, joint_vel_cmd); isOk = result == KortexErrorCodes.SUB_ERROR_NONE; else result = coder.ceval('kapi_SendJointSpeeds', obj.apiHandle, ... coder.ref(joint_vel_cmd), uint32(obj.nbrJointActuators)); isOk = result == KortexErrorCodes.SUB_ERROR_NONE; end end

2. Or instead, should I use the existing SendPreComputedTrajectory() function by:

Setting position(:, i+1) = position(:, i) + velocity(:, i) * dT; Keeping acceleration as zeros Setting a fixed dT and corresponding timestamp_sec array

I would appreciate any guidance on which approach is preferred, especially for real-time deployment or when using code generation.

Thanks in advance!

Best Regards,

Answer 1

[Shishir Reddy]

Hi Sanket

The current 'kortex.m' interface from the Simulink example does not include a method to send joint velocities directly, which is essential for real-time IBVS (Image-Based Visual Servoing).

Since your control law outputs joint velocities, the best approach is to extend the 'kortex.m' System object to include a method like 'SendJointSpeeds' as shown below.

function [isOk] = SendJointSpeeds(obj, joint_vel_cmd)
    if coder.target('MATLAB')
        % Use MEX interface during simulation
        [result] = kortexApiMexInterface('SendJointSpeeds', ...
                    obj.apiHandle, joint_vel_cmd);
        isOk = result == KortexErrorCodes.SUB_ERROR_NONE;
    else
        % For code generation (Simulink Real-Time, etc.)
        result = coder.ceval('kapi_SendJointSpeeds', ...
                    obj.apiHandle, ...
                    coder.ref(joint_vel_cmd), ...
                    uint32(obj.nbrJointActuators));
        isOk = result == KortexErrorCodes.SUB_ERROR_NONE;
    end
end

This allows you to send joint velocity commands directly to the robot using Kinova’s low-level API.

For more information, kindly refer the following example - https://www.mathworks.com/help/robotics/robotmanipulator/ug/connect-gen3-simulink.html

I hope this helps.