The Computer Assisted Design of the Industrial Transfer Robot Utilized Within the Bb-01

THE COMPUTER – ASSISTED DESIGN OF THE INDUSTRIAL TRANSFER ROBOT UTILIZED WITHIN THE BB-01 FLEXIBLE LINE OF PRODUCTION

D. G. Zisopol, Ph. D. Eng.*, A. A. Cazan**, Eng.

* “Petroleum - Gas” University of Ploiesti, Romania; ** Snamprogetti Romania

1 Introduction

The actual signification given to the concept of Flexible Line of Production relies on the idea of association – an association of some numerical control machine tools and a number of industrial robots, the said association representing a single whole deriving profit from the facilities offered by the electronics. The new concept concerning the Flexible Line of Production also supposes all subsystems (i. e. machining capabilities, logistics and controls) to be completely integrated and coordinated [4].

Given the above – specified circumstances, this paper shows the results offered by the computer – assisted design of the Industrial Transfer Robot utilized within the BB-01 Flexible Line of Production. The robot is mobile, suspended, equipped with arms having more articulations (“anthropomorphous” arms), flexibly programmed and electrically operated.

The BB-01 Flexible Line [7] is a Flexible Cell of Production being used within the mass production of the revolution parts belonging to the shaft class. The said flexible line consists of six Flexible Machining Units equipped with machine tools, which are controlled through a process computer; three Flexible Machining Units have lathes and the other three units have grinding machines.

The working system of the BB-01 Flexible Line includes three RI robots [1,7] loading the Flexible Line, three RT Transfer Robots [1] and three RMD Robots for Measurements and Defect Detection [1].

2 THE COMPUTER – ASSISTED DESIGN OF THE TRANSFER ROBOT

The authors of the paper utilized the AutoCAD 2002 Programme to design the geometric models of the Transfer Robot and the 3D Studio Programme to stimulate the operation of the Transfer Robot. The 3D Studio Programme also provided the multimedia support necessary to the easy understanding of the operational role specific to the robot components and offered the information related to the dynamics of the whole system.

The techniques of interactive graphics having been used were those usually applied for components, parts and assemblies of equipment to be utilized in mechanics, electricity, electromechanics and electronics.

The architecture of the Transfer Robot (see Fig. 1) is precise, the robot is articulated and its operation is feasible through rotational couplings whose axes are parallel (i. e. the axis ART 1, the axis ART 2 and the axis ART 3). The fourth rotational coupling (see Fig. 1), whose axis ART 4 is perpendicular to the axes of the above – mentioned couplings, permits the three arms of the robot to rotate simultaneously to handle the parts loaded and unloaded within the six Flexible Machining Units belonging to the
BB-01 Flexible Line of Production. The cavity of the Transfer - Robot arm (see Fig. 1) accommodates the seat of the Robot for Measurements and Defect Detection [1].

The Transfer Robot is equipped with five electric step-by-step motors controlled by the Process Computer of the BB-01 Flexible Line of Production (on the basis of the computation algorithm elaborated for the parameters afferent to the robot motion) through the Operating Lines afferent to each robot arm.

The seventeen sensors representing the Sensory System of the Transfer Robot provide that operating system with its feedback and give information about the angle of rotation, the angular speed and the angular acceleration of the components, the load being handled and the tightening moment applied to the part (to be handled) through the prehension components (fingers) of the robot.

The sensors of the Transfer Robot emit signals being transmitted to the Sensory Interface connecting with the Process Computer and the operating programme of the BB-01 Flexible Line of Production through the Sensory Line. The Process Computer compares the signals received from the Sensory System of the Transfer Robot with the standard values given by the tables containing the robot parameters. At the same time, the Process Computer elaborates the answers permitting the deviation elimination to be achieved and transmits the controls corresponding to each robot through the Operating Lines afferent to it.

Figure 1 - The construction of the Transfer Robot.

ART 1 – the rotational coupling of the socle; ART 2 – the lower coupling of the transfer arm;

ART 3 – the lower coupling of the transfer forarm; ART 4 – the hand articulation

See Figure 2 for the dimensions of the Transfer Robot.

Figure 2 - The dimensions of the Transfer Robot

See the operational and constructive specifications of the Transfer Robot below.

Table 1 - Operational and constructive specifications of the Transfer Robot

Operational and Constructive Specifications / Unit
of Measure / Value
Overall dimensions (h x b x L) / mm / 200 x 600 x 2,250
Raising capacity / g / 10,000
Positioning precision / mm / +/- 0,100
Degrees of mobility / - / 3,000
Degrees of freedom / - / 3,000
Position repeatability / - / 0,050
Volume of the working space / m3 / 4,128
The weight of the robot / kg / 115,000
Index of efficiency and flexibility / m3/kg / 0,040
Index of the handling capacity / - / 0,076
Total index / m3/mm / 3,123

The logical scheme shown in Figure 3 characterizes the motion of the Transfer Robot as a succession of working positions specific to the point M (i. e. the end of the prehension component belonging to the Transfer Robot) within a total system of coordinates.

Figure 3 - The succession of working positions specific to the point M afferent to the Transfer Robot

The Transfer Robot is activated when the cutting operations being achieved through the automatic lathe of the BB-01 Flexible Line of Production are over. The said robot grips the part being held by the fixing device of the automatic lathe and raises it up to the safety plane; after that, rotating the socle bearing the arms of the Transfer Robot (see Fig. 1) permits the part to be brought to the loading position of the grinding machine equipping the BB-01 Flexible Line of Production. The grinding machine is loaded and then, the Transfer Robot is raised up to the safety height. After the part is ground, the arm of the Transfer Robot will be held in the same position (the safety plane) as long as the Robot for Measurements and Defect Detection will be operated (the Robot for Measurements and Defect Detection is a stationary, articulated robot suspended and attached to the arm of the Transfer Robot; it is electrically operated [1] and includes flexible off – line and / or teach – in programming capabilities).

Finally, when the measurements and the defect detection are over, the Transfer Robot will raise the part from the fixing system of the grinding machine up to the safety plane and (if required) set it either on the conveying belt removing the finite parts having been admitted or on the checking table for defective finite parts, when the specialists of the Quality Control Department decide: those parts are either recoverable or not [1].

After the delivery of the finite parts, the Transfer Robot will be retrieved within the safety plane to wait for new working cycles.

See the articulation coordinates of the rotational couplings (table 2); it comes to the articulation coordinates corresponding to:

− either those working points where the parts are fixed within / delivered out of the Flexible Unit of Production (three Flexible Units of Production have lathes and the other three Units include grinding machines)

− or those working points afferent to the system evacuating the finite parts.

Table 2 - The articulation coordinates of the rotational couplings,

corresponding to the working points of the Transfer Robot

Type
of Robot / Working Point / Angle of Rotation
(articulation coordinates) [0] / Comments:
ART 1 / ART 2 / ART 3 / ART 4
R.T. / 1 / 0 / 0 / 0 / 0 / the neutral position
2 / 60 / 0 / 0 / 0 / the vertical position
of the lathe
3 / 60 / 8 / 56 / 56 / unloading of the lathe
4 / 0 / 9 / 56 / 56 / loading of the grinding
machine
5 / 0 / -13 / 67 / 67 / delivery of the finite part

The laws governing the motion of the kinematic couplings were determined through the synthesis of the relative motion specific to the trajectory generating mechanism, that determination being conditioned by the knowledge of all displacements induced to the characteristic point M of the Transfer Robot [1]. A system of polar coordinates is attached to each articulation because the motions performed by the Transfer Robot are complex. Any position of the characteristic point M is reached as a result of three simultaneous rotations of the robot elements. So, the programme permitting the robot to be operated sets the motion parameters by considering the articulation coordinates specific to each position of the elements belonging to the Transfer Robot.

See the motion parameters of the socle bearing the Transfer Robot below; the said parameters are expressed in articulation coordinates of the coupling ART 1.

Table 3 - Motion parameters of the socle bearing the Transfer Robots

Trajectory / Angle of Rotation
[0] / Angular Speed
[0/s] / Angular
Acceleration
[0/s2] / Displacement
Duration
[s]
0 / 1 / 2(1/4) / 3(2/4) / 4
1g2 / 60 / 1 / 0,017 / 60
2g3 / 0 / 0 / 0,000 / 70
3g2 / 0 / 0 / 0,000 / 70
2g1 / 60 / 1 / 0,017 / 60
1g4 / 0 / 0 / 0,000 / 55
4g1 / 0 / 0 / 0,000 / 55
1g4 / 0 / 0 / 0,000 / 55
4g5 / 0 / 0 / 0,000 / 35
5g1 / 0 / 0 / 0,000 / 40
TOTAL / 500

Table 4 shows the motion parameters afferent to the arm of the Transfer Robot, the said parameters being expressed in articulation coordinates of the coupling ART 2.

Table 4 - Motion parameters of the Transfer – Robot arm

Trajectory / Angle of Rotation
[0] / Angular Speed
[0/s] / Angular
Acceleration
[0/s2] / Displacement
Duration
[s]
0 / 1 / 2(1/4) / 3(2/4) / 4
1g2 / 0 / 0,000000 / 0,000 / 60
2g3 / 8 / 0,114286 / 0,002 / 70
3g2 / 8 / 0,114286 / 0,002 / 70
2g1 / 0 / 0,000000 / 0,000 / 60
1g4 / 9 / 0,163636 / 0,003 / 55
4g1 / 9 / 0,163636 / 0,003 / 55
1g4 / 9 / 0,163636 / 0,003 / 55
4g5 / 22 / 0,628571 / 0,018 / 35
5g1 / 13 / 0,325000 / 0,008 / 40
TOTAL / 500

Table 5 shows the motion parameters afferent to the forarm of the Transfer Robot, the said parameters being expressed in articulation coordinates of the coupling ART 3.

Table 5 - Motion parameters of the Transfer – Robot forarm

Trajectory / Angle of Rotation
[0] / Angular Speed
[0/s] / Angular
Acceleration
[0/s2] / Displacement
Duration
[s]
0 / 1 / 2(1/4) / 3(2/4) / 4
1g2 / 0 / 0,000000 / 0,000 / 60
2g3 / 56 / 0,800000 / 0,011 / 70
3g2 / 56 / 0,800000 / 0,011 / 70
2g1 / 0 / 0,000000 / 0,000 / 60
1g4 / 56 / 1,018182 / 0,019 / 55
4g1 / 56 / 1,018182 / 0,019 / 55
1g4 / 56 / 1,018182 / 0,019 / 55
4g5 / 11 / 0,314286 / 0,009 / 35
5g1 / 67 / 1,675000 / 0,042 / 40
TOTAL / 500

Table 6 shows the motion parameters afferent to the hand of the Transfer Robot, the said parameters being expressed in articulation coordinates of the coupling ART 3.

Table 6 - The motion law for MT i (i = 1…3)

3 CONCLUSIONS

The authors of this paper utilized the computer – assisted design method to show the results related to the dimensions and the operational and constructive specifications of the components belonging to the Transfer Robot. The Transfer Robot is mobile, suspended, equipped with arms having more articulations (“anthropomorphous” arms), electrically operated and flexibly programmed. The above – specified robot works within the BB-01 Flexible Line of Production.

SUMMARY

This paper covers the results of the research activity related to the computer – assisted design of the RT Industrial Transfer Robot as a component of the BB-01 Flexible Line of Production utilized within the mass production of the revolution parts belonging o the shaft class. The authors used techniques of interactive graphics specific to the components, parts and assemblies of equipment working in mechanics, electricity, electromechanics and electronics.

REFERENCES

1. Cazan A. A., Zisopol D. G. Research Regarding the Computer – Assisted Design of the BB-01 Flexible Line Utilized to Cut Revolution Parts, the Journal of “Petroleum - Gas” University of Ploiesti, Technical Series, Ploiesti, 2002.

2. Cojocaru G., Kovacs F. Industrial Robots in Action, Facla - Publishing House, Timisoara, 1986.