Parallel Robot Introduction
The major researches that have been done in the Parallel Robots team include :
Optimal design, kinematic and dynamic analysis, control and implementation of a planar cable driven parallel manipulator
Cable-driven parallel manipulators (CDRPMs) are a special class of parallel robots in which rigid extensible links are replaced by actuated cables. This type of parallel manipulators has several attractive features and some advantage such as large workspace, high payload-to-weight ratios, and low inertial properties, compared to those of conventional parallel manipulators. Having these desirable characteristics, cable robots have potential for many real world applications such as heavy payload handling, manufacturing operations, automated construction systems, high-speed manipulation and locomotion interfaces. Besides many advantages and promising potential, there are some new challenges in designing and development of cable manipulators.
- Workspace analysis of cable-driven redundant parallel manipulators
Workspace analysis is always one of the essential tasks in designing any mechanism. However, the unidirectional constraint imposed by cables makes this analysis more challenging for CDRPMs. In the literature, different types of workspace have been introduced based on various deﬁnitions for cable-driven parallel manipulators. In ARAS group, a set of newly deﬁned fundamental wrenches that opens new horizons to physical interpretation of controllable workspace of a general cable-driven redundant parallel manipulator is introduced. Based on this set of fundamental wrenches, a novel tool is presented to determine conﬁgurations of cable-driven redundant parallel manipulator that belong to the controllable workspace.
- Loloei, Azadeh Zarif, and Hamid D. Taghirad. “Controllable workspace of cable-driven redundant parallel manipulators by fundamental wrench analysis.”Transactions of the Canadian Society for Mechanical Engineering 3 (2012): 297-313.
- Khalilpour, S. A., et al. “Kinematic performance indices analyzed on four planar cable robots via interval analysis.”Robotics and Mechatronics (ICRoM), 2013 First RSI/ISM International Conference on. IEEE, 2013.
- Loloei, Azadeh Zarif, Mohamad M. Aref, and Hamid D. Taghirad. “Wrench feasible workspace analysis of cable-driven parallel manipulators using LMI approach.”Advanced Intelligent Mechatronics, 2009. AIM 2009. IEEE/ASME International Conference on. IEEE, 2009.
- Control of CDRPMs Considering Elastic Cables
Unlike the rigid links, cables can only apply tensile forces and therefore they shall be kept in tension in the whole workspace of the robot and as soon as the cables become slack, the structure of the cable robot collapses. Due to above mentioned physical limitation, well-known control theories cannot be used directly for CDPMs and they must be modiﬁed to provide positive tension for the cables.
Control of fully constrained parallel cable robots with elastic cables is studied by ARAS group. Since both the capability of the cable robot to achieve high accuracy in positioning and its vibrations depend directly on the control scheme of the system, investigation of the control and the stability in parallel robots with elastic cables is of particular importance.
Selected Papers :
- Khosravi, Mohammad A., and Hamid D. Taghirad. “Robust PID control of fully-constrained cable driven parallel robots.”Mechatronics 2 (2014): 87-97.
- Khosravi, Mohammad A., and Hamid D. Taghirad. “Dynamic analysis and control of cable driven robots with elastic cables.”Transactions of the Canadian Society for Mechanical Engineering 4 (2011): 543-558.
- Khosravi, Mohammad A., and Hamid D. Taghirad. “Dynamic modeling and control of parallel robots with elastic cables: singular perturbation approach.”IEEE Transactions on Robotics 3 (2014): 694-704.
- Babaghasabha, Reza, Mohammad A. Khosravi, and Hamid D. Taghirad. “Adaptive robust control of fully constrained cable robots: singular perturbation approach.”Nonlinear Dynamics 1 (2016): 607-620.
- Babaghasabha, Reza, Mohammad A. Khosravi, and Hamid D. Taghirad. “Adaptive robust control of fully-constrained cable driven parallel robots.”Mechatronics 25 (2015): 27-36.
Figure 1 : Prototype of a planar cable driven robot fabricated at K. N. Toosi University of Technology.
Figure 2: Interval analysis representation of controllable workspace of a planar cable driven robot
Figure 3: Block diagram of a cable driven robot control
Delta is a high precision parallel robot platform which can reach high accelerations that make it suitable for the production line as a pick and place robot. The mechanism consists of three identical branches comprising a parallelogram mechanism with spherical joints which are coupled to the actuator links via revolute joints.
Optimal design and implementation of a Delta robot for rapid pick and place application have been done by ARAS group. Kinematic and dynamic formulations have been established and according to them an optimal structure of the mentioned robot has been yield according to the kinematics indexes and dynamic limitations. Trajectory planning and time optimal trajectory planning have been proposed to reach the highest permissible rate of pick and place operation per minute. Further information about the research project and a movie of the KNTU Delta Robot is available here.
Khorasani, Amin, Soheil Gholami, and Hamid D. Taghirad. “Optimization of KNTU Delta robot for pick and place application.” Robotics and Mechatronics (ICROM), 2015 3rd RSI International Conference on. IEEE, 2015.
Control of suspended CDR considering cables dynamics
Deployable cable driven robot
Over the last decade, many researches have studied in the field of cable robots, but still their applications are very limited compared to the conventional serial robots. Introducing a simple and deployable design for the cable driven robots may significantly influence their wider use in industrial applications. This causes the installation of the robot is not be limited to a fixed and well calibrated structure and high accuracy calibration process is no longer required. By this means the robot may be easily moved from one place to another. Such designs are considered to have rapidly deployable characteristics, which makes them more applicable. In deploy-able cable driven robots, kinematic dimensions and parameters of the robot is not accurately measured, and this uncertainty in the measurement will appear in the most of the robots model parameters. This introduces many challenges in terms of the controller design with the required performance for the designer. The goal of this project is to develop a theoretical framework for robust position control of CDPMs. To develop the idea, modeling uncertainties are taken into account and robust stability of the closed-loop system with proposed control algorithm is performed.
Sensor fusion application in control of cable driven robot
Kinematic and dynamic calibration of deployable suspended cable driven robot
Since the positions of the cable attachment points in deployable robot are not accurately available, the forward kinematics of the robot would not provide an accurate value for the end effector position. In order to improve the accuracy of the forward kinematic solutions, at the first step the parameters by which the accuracy of the robot is greatly affected are identified. For this purpose, an analysis on parameter sensitivity is presented and effective parameters are introduced. Then, based on these parameters and by using the redundant equations of the DSCDPM, a new set of equations for the forward kinematic analysis are derived.
Cable force measurement
Salman’s academic background is on mechanical engineering. His interest in interdisciplinary field of engineering, specially robotics urged him to develop some skills in designing and implementation of mechatronic systems. His contribution in ARAS was to implement suspended cable platform and design portable low cost sensors for cable tension measurement. Currently he is CTO at ASYP, a company working on emerging robotic technologies.