#HEXA 6 ROBOT SERIAL#
#HEXA 6 ROBOT SOFTWARE#

2 The environmental illumination should be carefully planned. The calibration method is simple, economical and easy to use, with good repeatability and acceptable precision to obtain accurate data, the following five important points must be considered carefully: 1 Camera and chessboard positioning and installation should be carried out delicately. Minimizing equation (12) is a nonlinear minimization problem, which is solved with the Levenberg–Marquardt algorithm (Zhang, 2000). K is the camera intrinsic parameters’ matrix and k i s are the distortion coefficients. m ˆ ͑ K, R i, T i, M j ͒ ( m is the real point and m ˆ is the estimated point) is the two-dimensional projection of the 3D point M in image i and R and T are the rotation and translation matrices, respectively. Equation (10) describes how a point in the environment maps to the image. It is a useful model that enables simple mathematical formulation for the relationship between object and image coordinates (Heikkila and Silvén, 1997). The pinhole model is only an approximation of the real camera projection. Figure 5 illustrates the pinhole camera model with the image plane located in front of the lens. The pinhole camera model is based on the principle of collinearity, where each point in the object space is projected by a straight line through the projection center into the image plane. One common way of modeling a camera is to use the pinhole camera model. The intrinsic camera parameters usually include the effective focal length, pixel size, distortion coefficient and the image center (Heikkila and Silvén, 1997). Extrinsic parameters are needed to transform object coordinates to a camera-centered coordinate frame. Physical camera parameters are commonly divided into extrinsic and intrinsic parameters. Additionally, a simple USB Video Graphics Array (VGA) camera connected to a computer, and a chessboard, installed on the mobile platform, are needed for the calibration procedure. This tiny processor reads the encoders’ data and sends the arms’ angles in a 6 1 vector to the computer and, at the same time, receives a 6 ϫ 1 command vector from the computer and uses them to drive the motors. A microcontroller, PIC18F452, is the central processor in the board that manages data transfer between the robot and the computer.

#HEXA 6 ROBOT SERIAL#

The connection between the Personal Computer (PC) and the robot is through the serial port input commands are sent from the PC to the motors, and arms’ angles are read from the encoders and then sent to the PC. To carry heavy loads (up to 10 kg), the motors are selected to yield a maximum torque of 63 Nm. The measured joint positions from encoders’ readings are provided with a filter program which is written to reduce noise. One incremental 3,000 (pulse/revolution) encoder is attached to each arm for calibration and control purposes. The ideal design lengths of the robot are given in Tables II–IV in their corresponding columns. Based on the designed parameters in the CAD software, the Hexa robot is fabricated and approved in Comet Trading Co., Shiraz ( Figure 4).

#HEXA 6 ROBOT SOFTWARE#

Base, end-effector, arms and rods are first drawn and assembled in Computer-aided Design (CAD) software to ensure the parts’ production precision.

For example, any deviation in the position or orientation of any motor in the base produces sensible error in its performance at the end-effector. To reduce the performance errors in a parallel robot, its dimensions should be precisely taken into account when fabricating. Note that the joint between L and M is a two-degrees-of-freedom universal joint, so that the link L does not necessarily lie in the plane of the figure. The joint angle ␪ i,j is variable and measured the lengths L and M of the “base” and “top” limbs of each chain are constant the angles of all other joints are variable but not measured. ͓ i, j i, j i, j 1 ͔ is the position vector of the pivot point t i in the reference frame constructed in the actuated R joint (Pierrot et al.

Hexa 6 robot