Browsing by Subject "Friction compensation"
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Item Open Access Mechanical design and position control of a modular mechatronic device (MechaCell)(IEEE, 2015) Ristevski, Stefan; Çakmakçı, MelihManufacturing techniques have advanced exponentially in recent years, providing means for production of smaller and more powerful electronics, which makes it compelling to design small and more powerful robots. Our work focuses on a mechanical design and position control of a modular mechatronic device called MechaCell. Mechacells are designed as modular semi-autonomous devices which can be used alone or part of a pack. In this paper our main focus is on the mechanical design of the Mechacell, especially the locomotion system which uses forces produced by a rotating unbalance that moves in a spherical domain for steering of the Mechacell. As part of the supervisory algorithm an overhead HD camera is used for position tracking of the Mechacell; the data is then sent to the Mechacells through a wireless connection. A proportional integral derivative controller is used as a base controller; then a friction compensation algorithm is added, based on the mathematical model of the Mechacell's locomotion system. Steering and locomotion controller of the Mechacell is validated using a complex motion profile in the developed testbed.Item Open Access Nonlinear identification and optimal feedforward friction compensation for a motion platform(Elsevier, 2020) Güç, Ahmet Furkan; Yumrukçal, Z.; Özcan, OnurIn this study, we present a method of nonlinear identification and optimal feedforward friction compensation for an industrial single degree of freedom motion platform. The platform has precise reference tracking requirements while suffering from nonlinear dynamic effects, such as friction and backlash in the driveline. To eliminate nonlinear dynamic effects and achieve precise reference tracking, we first identified the nonlinear dynamics of the platform using Higher Order Sinusoidal Input Describing Function (HOSIDF) based system identification. Next, we present optimal feedforward compensation design to improve reference tracking performance. We modeled the friction using the Stribeck model and identified its parameters through a procedure including a special reference signal and the Nelder–Mead algorithm. Our results show that the RMS trajectory tracking error decreased from 0.0431 deg/s to 0.0117 deg/s when the proposed nonlinear identification and friction compensation method is utilized.Item Open Access Nonlinear identification and optimal feedforward friction compensation for a motion platform(Bilkent University, 2020-06) Güç, Ahmet FurkanWe present a method of nonlinear identification and optimal feedforward friction compensation procedure for an industrial single degree of freedom motion platform. The platform suffers from nonlinear dynamic effects, such as friction and backlash in the driveline, along with precise reference tracking requirements. In order to eliminate the nonlinear dynamic effects and obtain precise reference tracking, we first identified the system using nonparametric identification with Best Linear Approximation (BLA). Next, the feedback controller is implemented as a classical PI controller and it is designed using loop shaping techniques so that the system meets the linear system requirements. Then, we identified the nonlinear dynamics of the platform using Higher Order Sinusoidal Input Describing Function (HOSIDF) based system identification and we present optimal feedforward compensation design to improve reference tracking performance. We modeled the friction characteristics using the Stribeck friction model and identified through a procedure with a special reference signal and the Nelder-Mead algorithm. Results indicate that the RMS trajectory error decreased from 0.0431 deg/s to 0.0117 deg/s, and standart deviation of speed reference error integral decreased from 0.0382 deg to 0.0051 deg, when the proposed nonlinear identification and friction compensation method is used.Item Open Access Planar motion controller design for a modular mechatronic device with heading compensation(Elsevier, 2019) Ristevski, Stefan; Çakmakçı, MelihMechaCells are designed as closed, scalable and modular semi-autonomous devices that can be used alone or part of a pack. In this paper, we discuss a locomotion system that uses the reaction force produced by a rotating unbalance that moves in a spherical domain with a steering mechanism. In order to produce the precise motion capability, a multi-loop controller is developed. This controller uses a friction compensation algorithm based on the mathematical model of the locomotion system. To improve the accuracy of tracking, conventional LuGre friction estimation model is extended for rapid directional changes of the MechaCell during planar motion. The linear and rotational acceleration of the device is also included in controller calculations since it affects the locomotion force generated by the unbalanced mass. The resulting control system is validated both with simulations and experiments and the effectiveness of the extended model and the controller is verified. Our results show significant improvement when a detailed friction compensation observer is used in the controller that includes the effect of sudden steering changes for precise path following.