Joint Control (RobotArm)

Joint control for a robotic arm means sending target angles to each joint or reading current angles, and moving under a given speed constraint until reaching the target. This document is based on RobotArm (include/RobotArm.hpp), for MyCobotPro450, with Linux + TCP communication (see Environment Setup and Build).

All interfaces below follow the same format: Function, Return Value, Parameter Description, and Range. For the full API index, see API Reference.

Joint Angle Ranges (°)

Speed sp / speed: 1 ~ 100 (same throughout this document).

Single Joint

int sendAngle(uint8_t joint, float angle, uint8_t sp)

• Function: Sends a target angle to the specified joint.
• Return Value: Usually 1 when communication and command succeed; usually -1 on failure (controller behavior prevails).
• Parameter Description: joint joint index; angle target angle (°); sp speed level.
• Range: joint: 1 ~ 6; angle: see table above; sp: 1 ~ 100.

Multiple Joints

float getAngle(uint8_t joint)

• Function: Reads the current angle of one joint.
• Return Value: Floating-point angle (°); may return sentinel values on abnormal conditions (per integration behavior).
• Parameter Description: joint.
• Range: joint: 1 ~ 6.

Angles getAngles()

• Function: Reads current angles of all six joints at once.
• Return Value: Angles (std::array<float, 6>), indices 0 ~ 5 correspond to J1 ~ J6.
• Parameter Description: None.
• Range: None.

int sendAngles(Angles angles, uint8_t sp)

• Function: Sends target angles for all six joints in one command.
• Return Value: Usually 1 on success, -1 on failure.
• Parameter Description: angles six target angles; sp speed level.
• Range: Each element follows the corresponding joint range in the table above; sp: 1 ~ 100.

float getJointMinAngle(uint8_t joint) / float getJointMaxAngle(uint8_t joint)

• Function: Reads software joint limits (min/max angle).
• Return Value: Floating-point value (°).
• Parameter Description: joint.
• Range: joint: 1 ~ 6.

JOG and Auxiliary

int jogAngle(uint8_t joint, uint8_t direction, uint8_t speed)

• Function: Continuously rotates the specified joint in one direction until a limit is reached or stop() is called.
• Return Value: Usually 1 on success, -1 on failure.
• Parameter Description: joint; direction; speed.
• Range: joint: 1 ~ 6; direction: 0 negative, 1 positive; speed: 1 ~ 100.

int setFreeMoveMode(bool state) / int getFreeMoveMode()

• Function: Enables/disables free-move mode (for manual guiding), or queries current status.
• Return Value: Set function usually returns 1 on success; query returns 0 off, 1 on, -1 on failure.
• Parameter Description: state, false/true.
• Range: Boolean mapping to 0 / 1.

int setMotorEnabled(uint8_t joint, bool state) / int servoRestore(uint8_t joint)

• Function: Enables/disables one joint motor, or clears joint abnormality (restore command).
• Return Value: Usually 1 on success, -1 on failure.
• Parameter Description: joint; setMotorEnabled also requires state (false disable torque, true enable torque).
• Range: joint: 1 ~ 6 or 254 (all joints).

In-Position and Closed-Loop (Used with Joint Commands)

int isInPosition(Angles angle_coords, bool mode)

• Function: Checks whether the robot has reached the given 6-axis target.
• Return Value: 1 reached; 0 not reached; -1 abnormal or no valid response.
• Parameter Description: angle_coords six target values; mode data type flag.
• Range: For joint-angle checks, use mode == false; angles follow the joint-angle table in this chapter.

void setWaitArrival(bool enable) / bool getWaitArrival() const / bool waitPosArrived(int timeout_ms = 30000)

• Function: Sets whether motion commands wait for arrival before returning; queries this switch; or blocks until arrival feedback.
• Return Value: setWaitArrival has no return value; getWaitArrival returns bool; waitPosArrived is true when arrived and false on timeout.
• Parameter Description: enable; timeout_ms timeout (ms).
• Range: timeout_ms > 0, default 30000.

Drag Teaching

int dragTeachSave() / int dragTeachPause() / int dragTeachExecute() / int dragTeachClean()

• Function: Start drag trajectory recording; pause recording; execute the recorded trajectory once; clear sampled points.
• Return Value: Usually 1 on success, -1 on failure.
• Parameter Description: None.
• Range: Recommended single recording duration ≤ 120 s.

Example (Excerpt)

The following example assumes TCP connectivity to the robot-side service is already available. It only demonstrates joint-related calls. Add error handling and thread-safety logic according to your project requirements.

#include "RobotArm.hpp"
#include "config.hpp"
#include <iostream>
#include <thread>
#include <chrono>

using namespace std::chrono_literals;

int main() {
    Param p;
    p.ip_serial = "192.168.0.232";
    p.port_baud = 4500;

    RobotArm arm(TCP_COMM, p);

    if (arm.powerOn() != 1) {
        std::cerr << "powerOn failed\n";
        return 1;
    }

    Angles cur = arm.getAngles();
    std::cout << "J1=" << cur[0] << " ...\n";

    Angles goal = {5.f, 5.f, 5.f, -5.f, 5.f, 5.f};
    if (arm.sendAngles(goal, 30) != 1) {
        std::cerr << "sendAngles failed\n";
    }

    while (arm.isInPosition(goal, false) != 1) {
        cur = arm.getAngles();
        std::cout << "J1=" << cur[0] << "\n";
        std::this_thread::sleep_for(200ms);
    }

    arm.jogAngle(1, 1, 30);
    std::this_thread::sleep_for(2s);
    arm.stop();

    arm.powerOff();
    return 0;
}

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