Calibrating the Arm

In the previous posts we talked about how we applied Inverse Kinematics and kinematic analysis of the mentor arm. As mentioned the arm consists with Potentiometers and DC motors and with the POTs we get a feedback on the angle and movement direction. In this post we will be talking on calibrating the arm. 

Indeed the reading from the POTs are consistent. And we don't have a control circuit to receive accurate readings. We are passing each POT readings through a digital low pass filter so it filters out the high frequency noise. Also there is a threshold value for pot readings (+/- 10) to avoid the overshoot. 

In the mentor arm there are physical limits to avoid gears getting damaged physically. In the code we will limiting the movement of each arm respect to the limits of the leap motion and including these physical limits. Also in the using the IK formulae calculated angles, will go to infinity if the distance of the palm and the leap origin is greater than the total length of Top arm and bot arm which is 31.5cm. So if the function "jointangles"outputs "NaN" (Not a Number - infinity) we ignore them.

Inverse Kinematics on MENTOR Arm - Part 2

As mentioned in the previous post we are using IK only for 2dof (on x and y plane). By that we calculated the joint angles on the Top and Bottom arm for the given x,y,z coordinates. 

Using the conversion from cartesian coordinate system (x,y,z) to cylindrical coordinates (ρ,theta2,r) the joint angle for base arm (theta2) was calculated.

Angle - Base arm

To calculate the joint angles the function "jointAngles" is used. The x,y,z coordinates of the palm that we get from the leap motion data are passed as an array "v" into the function and theta2 - base angle, angle2 - Bottom angle and angle3 - Top angle are returned as the output. 

Inverse Kinematics on MENTOR Arm

In this article we will talk about using inverse kinematics on the Mentor arm. The purpose of this is to position the wrist position of the Mentor Arm according to the x,y,z coordinates that we get from leap motion (will be discussed in a future post). 

Figure 1: Overview of Palm position and the wrist position