The second period starts in 1985 when S. G. Tzafestas moved as a Control and Robotics Professor to the Electrical and Computer Engineering School of the National Technical University of Athens, where he established the Intelligent Robotics and Automation Laboratory.

The main research areas of this period are:

  1. Robotic systems
    From 1985 when S.G.Tzafestas moved from Patras University to NTUA, he turned his interest to robotic systems and intelligent control. The results of his research include a number of important novel techniques and systems. This activity was started with industrial manipulators and has been extended to autonomous mobile robots. The particular topics investigated are: kinematic and dynamic modeling, robot parameter identification from input-output data, autonomous trajectory generation, robot cell modeling via Petri nets, on-line discrete-time control, resolved motion MBP control, adaptive control, robust control, flexible-joint and flexible-link robot modeling and control, stability analysis; mobile robot path and motion planning in structured, unstructured and time-varying environments; robot tactile sensing and 2D-3D object recognition. The applications include assembly/ disassembly and welding. In this area he has also investigated the status of robotics education in Europe, and has published the following contributed reference books:
    1. Intelligent Robotic Systems, Marcel Dekker, N.Y. (1991).
    2. Microprocessors in Robotic and Manufacturing Systems, Kluwer (1991).
    3. Robotic Systems: Techniques and Applications, Kluwer (1992).
    4. Progress in System and Robot Analysis and Control Design, Springer, London/Berlin (1999) (with G.Schmidt).
    5. Advances in Intelligent Autonomous Systems, Kluwer, Dorhrecht/Boston (1999).
    6. Innovations in Robot Mobility and Control, Springer, Berlin (2006) (with S.Patnaik, L.C.Jain, G.Resconi and A.Konar).

    Key Publications

    1. Integrated sensor-based intelligent robot system, IEEE Control Syst. Magaz., Vol.8, pp.61-72 (1988).
    2. Robot model reference adaptive control through lower/ upper part dynamic decomposition, J.Intell. & Robotic Syst., Vol.1, pp.163-184 (1988).
    3. Combined computed torque and model reference adaptive control of robot systems, J.Franklin Inst., Vol.327, pp.273-294 (1990).
    4. Robust stability analysis of robot control systems, Robotics & Autonomous Systems, Vol.7, pp.285-290 (1991).
    5. Some results concerning the autonomous trajectory generation and adaptive control of industrial robots, J.Franklin Inst., Vol.329, No.1, pp.1-14 (1992).
    6. Resolved motion model-based predictive control of redundant robots, Maths.& Computers in Simul., Vol.37, pp.195-205 (1994).
    7. Analysis and design of a new piezoresistive tacticle sensor system for robotic applications, J.Intell. & Robotic Syst., Vol.10, pp.243-256 (1994).
    8. On-line discrete-time control of industrial robots, Robotics & Autonomous Systems, Vol.14, pp.289-299 (1995).
    9. Robust sliding mode control applied to a 5-link biped robot, J.Intell. & Robotic Syst, Vol.15, No.1, pp.67-133 (1996).
    10. Robust control and motion design for mobile robots in a time-varying environment, Proc IMACS/ IEEE Symp. on Robotics & Cybernetics, Lillie, France, July (1996).
    11. The active kinematic histogram method for path planning of non-point, non-holonomically constrained mobile robots, Advanced Robotics, Vol.12, No.4, pp.375-395 (1998).
    12. Mobile robot motion control in partially unknown environments using a sliding-mode fuzzy logic controller, Robotics and Autonomous Systems, Vol.33, No.1, pp.1-11 (2000).
    13. Human like behavior of robot arms (I) Robotics and Comp. Integrated Manuf., Vol.17, pp.305-315; (II), ibid, Vol.17, pp.317-327 (2001).
    14. Robust motion planning and control of mobile robots for collision avoidance in terrains with moving objects, Maths & Computers in Simul., Vol.59, No.4, pp.279-292 (2002).
    15. A robust fuzzy-logic path tracker for non holonomic mobile robots, Intl. J. Artif. Intell. Tools, Vol.14, No.6, pp.935-965 (2005).
  2. Management and control of manufacturing systems
    The work in this area was carried-out simultaneously with the work in robotics and has been motivated by European projects and practical issues. The problems considered include: discrete event modeling, optimization of transshipment operations, CIM product multisupplier / multi-distributor chains, CIM inventory and production planning and control, manufacturing task scheduling, autonomous car disassembly, GMA welding parameter regulation, and AI- and knowledge- based design of manufacturing systems. In this area he has edited the following reference books:
    1. Optimization and Control of Dynamic Operational Research Models, North-Holland (1982).
    2. Robotics and Flexible Manufacturing Systems, Elsevier (1992).
    3. Computer-Assisted Management and Control of Manufacturing Systems, Springer (1996).
    4. Advances in Manufacturing: Decision, Control and Information Technology, Springer (1999).

    Key Publications

    1. Deadbeat time-optimal control of production-inventory systems, Found Control Engrg., Vol.4, pp.173-188 (1979).
    2. Integrated approach to computer-aided multi-supplier/ multi-distributor operations in the automotive industry, Proc. 23rd Intl. Symp. on Automotive Technology and Automation (ISATA '90), Vienna, pp.264-273 (1990).
    3. Optimal task scheduling via the LPT and MULTIFIT heuristics under a geometric progression condition, Found. Comp&Decision Sci., Vol.17, No.2, pp.99-107 (1992).
    4. A new adaptively weighted combinatorial dispatching rule for complex scheduling problems, Computer- Integrated Manufacturing Systems, Vol.7, No.1, pp.7-15 (1994).
    5. Hierarchical control approach to managerial problems of manufacturing systems, In: Modern Manufacturing-Information, Control and Technology (M.Zaremba and B.Prasad, eds), Springer, pp.173-224 (1994).
    6. Coordinated control of manufacturing supply chains, Computer-Integrated Manufacturing Systems, Vol.7, No.3, pp.206-212 (1994).
    7. Flexible Petri nets for intelligent robot cell modeling, Found Computing & Decision Sci, Vol.20, No.3, pp.239-252 (1995).
    8. Model-based predictive control for managerial planning in a composite marketing-production problem, Stud. Informatics & Control (SIC), Vol.4, No.1, pp.59-78 (1995).
    9. Integrated approach to dynamic production inventory and marketing decisions in multi-product CIM operations, Syst. Anal. Model. Simul. (SAMS), Vol.17, pp.1-19 (1995).
    10. Petri-net-based approach to the synthesis of intelligent control for discrete-event dynamic systems (DEDS), In: Management and Control of Manufacturing Systems, Springer (1996).
    11. Architecture and implementation of an autonomous car-disassembly system, Syst. Anal.Model.Simul., Vol.29, No.2, pp.153-186 (1997).
    12. Geometry and thermal regulation of GMA welding via conventional and neural adaptive control, J.Intell.&Robotic Syst., Vol.19, No.2, pp.153-186 (1997).
    13. Regulation of GMA welding thermal characteristics via a hierarchical MIMO predictive control scheme assuring stability, IEEE Trans. Indust. Electron, Vol.47, No.3, pp.668-678 (2000).
  3. Artificial intelligence and knowledge-based systems
    The work in this field was started in 1987. The main topic investigated with important original results and practical software tools is system fault diagnosis for technological systems including some medical problems. Other topics extensively studied are: knowledge acquisition, attribute grammars, probabilistic inference, nonmonotonic reasoning, shallow and deep reasoning, certainty factors models, multiagent architectures, and inductive learning. The applications include, besides fault diagnosis: polynomial function discovery, industrial process data rejection/filtering for SCADA applications, decision making, business processes, expert control and supervision, robot task/path planning, object recognition, and CAD/CAM. In this area S.G.Tzafestas has also published a number of comprehensive timely surveys and has edited the following reference books:
    1. Knowledge-Based System Diagnosis, Supervision and Control, Plenum Press (1989).
    2. Engineering Systems with Intelligence: Concepts, Tools and Applications, Kluwer (1991).
    3. Expert Systems in Engineering Applications, Springer (1993).
    4. Artificial Intelligence in Industrial Decision Making, Control and Automation, Kluwer (1995).
    5. Knowledge-Based Systems: Advanced Concepts, Techniques and Applications, World Scientific (1996).
    6. Methods and Applications of Intelligent Control, Kluwer (1997).
    7. Advances in Intelligent Systems, Kluwer (1999).

    Key Publications

    1. A framework for knowledge-based control, J.Intell. and Robotic Syst., Vol.2, pp.407-425 (1989).
    2. System fault-diagnosis using the knowledge-based methodology, in: Fault Diagnosis in Dynamic Systems (R.Patton, P.Frank and R.Clark, eds), Prentice Hall, pp.509-572 (1989).
    3. A numeric-symbolic expert system for 2-D and 3-D object recognition in robotic applications, Maths and Computers in Simul., Vol.32, pp.403-418 (1990).
    4. AI techniques in computer-aided manufacturing systems, in: Knowledge Engineering (H.Adeli, ed), McGraw Hill, pp.161-212 (1990).
    5. Second-generation diagnostic expert systems: Requirements, architectures and prospects, Proc SAFEPROCESS '91: IFAC/IMACS Intl.Symp. on Fault-Detection and Safety for Technical Processes, Baden-Baden, Germany, Sept (1991).
    6. ENGEXP: An integrated environment for the development and application of expert systems in equipment and engine fault diagnosis and repair, Advances in Engrg Software, Vol.14, No.1, pp.3-14 (1992).
    7. ESID: An expert system for diagnosis and therapy of infectious diseases, Syst.Anal.Modelling Simul., Vol.9, No.1, pp.1-21 (1992).
    8. Knowledge-based expert systems for intelligent control applications, in: Expert Systems in Engineering Applications, Springer, pp.259-268 (1993).
    9. Diagnostic expert system inference engine based on the certainty factors model, Knowledge-Based Systems, Vol.7, No.1, pp.17-26 (1994).
    10. A real-time expert data filtering system for industrial plant environment, Maths and Computers in Simul., Vol.41 (1996).
    11. A polynomial function discovery system: FFS, Intl.J Artificial Intell.Tools (IJAIT), Vol.6, No.1, pp.1-13 (1997).
    12. Architectural and functional issues of a decision support expert system for concurrent design, in: Knowledge Based Systems – Advanced Concepts Techniques and Applications, World Scientific, Singapore, pp.87-124 (1997).
    13. Multi-agent robot architectures: The decomposition issue and a case study, Intl. J.Artif.Intell.Tools, Vol.7, No.2, pp.163-187 (1998).
    14. A hybrid pricing expert system based on fuzzy reasoning, Found. Comp.& Decisions Sci, Vol.24, No.4, pp.171-187 (1999).
    15. Improving business processes with the use of knowledge-based systems, in: Recent Developments and Applications in Decision Making (S.Zanakis et.al.eds), Kluwer, Boston (2000).
  4. Fuzzy, neural and neuro-fuzzy systems
    The work in the applied soft-computing or computational intelligence area has started in 1988. Both theoretical and practical issues of fuzzy, neural, and neuro-fuzzy networks have been investigated. The theoretical topics include: fuzzy and neural learning, NN generalization capability, overtraining phenomenon, reinforcement structures, generalized fuzzy inference, fuzzy parameter and state estimation, fuzzy dynamic systems (input-output and state space analysis); level-2 fuzzy reasoning; fuzzy, neural and neuro-fuzzy control; multi-network architectures, neuro-fuzzy agent-like architectures, fuzzy algorithms using quantum computation, and neural associative memories using quantum learning. The applications include fuzzy PID control of industrial systems, multi-link industrial manipulators, robotic fruit collectors, adaptive (self-tuning) control of CARMA systems, mobile robot path planning, robotic assembly processes, neurocontrol of large scale systems, and fault diagnosis of chemical and technological processes. Books published in this area include:
    1. Fuzzy Reasoning in Information Decision and Control Systems, Kluwer, Dordrecht/Boston (1994) (with A.N.Venestanopoulos).
    2. Soft Computing in Systems and Control Technology, World Scientific, Singapore/London (1999).
    3. Computational Intelligence in Systems and Control Design and Applications, Kluwer, Dordrecht/Boston (1999).

    Key Publications

    1. Incremental fuzzy expert PID control, IEEE Trans on Industrial Electronics, Vol.37, No.5, pp.365-371 (1990).
    2. Learning algorithms for neural networks with the Kalman filters, J.Intell.& Robotic Syst., Vol.3, No.4, pp.305-319 (1990).
    3. Fuzzy systems and fuzzy expert control: An overview, The Knowledge Engineering Review, Vol.9, No.3, pp.229-268, (1994).
    4. An investigation of the application of neural networks to the diagnosis of chemical engineering processes, Proc.Intl.Symp. on Signal Processing, Robotics and Neural Networks, Lille, France, April (1994).
    5. A fuzzy path planning algorithm for autonomous robots moving in an unknown and uncertain environment, Proc.Europ.Robotics and Intelligent Systems Conf., Malaga, Spain, Vol.1, pp.140-149, Aug. (1994).
    6. Learning multiple fuzzy control for robot manipulators, J.Artificial Neural Networks, Vol.2, Nos. 1&2, pp.119-136 (1995).
    7. Fuzzy-neural network controllers using mean-value-based functional reasoning, Neurocomputing, Vol.9, pp.39-61 (1995).
    8. On the overtraining phenomenon of back-propagation neural networks, Maths & Computers in Simul., Vol.40, Nos.5-6, pp.1-15 (1996).
    9. A flexible neurofuzzy cell structure for general fuzzy inference, Maths & Computers in Simul., Vol.41 (1996).
    10. Artificial neural networks in the fault diagnosis of technological systems: A case study in a chemical engineering process, Engrg.Simul.J. (1996).
    11. Graph coloring using fuzzy controlled neural networks, Intell.Autom.and Soft.Computing, Vol.4, No.4, pp.273-288 (1998).
    12. Industrial robot navigation and obstacle avoidance employing fuzzy logic, J.Intell.& Robotic.Syst., Vol.27, Nos.1-2, pp.85-97 (2000).
    13. NeuroFAST: An on-line neuro-fuzzy ART-based structure and parameter learning Takagi-Sugeno-Kang model, IEEE Trans.Syst.Man.Cybern-PartB, Vol.31, No.5, pp.797-802 (2001).
    14. Parallelization of a fuzzy control algorithm using quantum computation, IEEE Trans.Fuzzy.Syst., Vol.10, No.4, pp.451-460 (2002).
    15. Quantum learning for neural associative memories, Fuzzy Sets & Systems, Vol.157, No.13, pp.1797-1813 (2006).