44 research outputs found
An innovative system for supplying air and fuel mixture to a combustion chamber of an engine
No full textResetting disturbance observers with application in compensation of bounded nonlinearities like hysteresis in piezo-actuators
No full textThis paper presents a novel nonlinear (reset) disturbance observer for dynamic compensation of bounded nonlinearities like hysteresis in piezoelectric actuators. Proposed Resetting Disturbance Observer (RDOB) utilizes a novel Constant-gain Lead-phase (CgLp) element based on the concept of reset control. The fundamental limitations of linear DOB which results in contradictory requirements and in a dependent design between DOB and feedback controller are analysed. Two different configurations of RDOB which attempt to alleviate these problems from different perspectives are presented and an example plant is used to highlight the improvement. Stability criteria are presented for both configurations. Performance improvement seen with both RDOB configurations compared to linear DOB is also verified on a practical piezoelectric setup for hysteresis compensation and results analysed.Accepted Author ManuscriptMechatronic Systems Desig
Complex order control for improved loop-shaping in precision positioning
No full textThis paper presents a complex order filter developed and subsequently integrated into a PID-based controller design. The nonlinear filter is designed with reset elements to have describing function based frequency response similar to that of a linear (practically non-implementable) complex order filter. This allows for a design which has a negative gain slope and a corresponding positive phase slope as desired from a loopshaping controller-design perspective. This approach enables improvement in precision tracking without compromising the bandwidth or stability requirements. The proposed designs are tested on a planar precision positioning stage and performance compared with PID and other state-of-the-art reset based controllers to showcase the advantages of this filter.Accepted Author ManuscriptMechatronic Systems Desig
Development of robust fractional-order reset control
No full textIn this paper, a framework for the combination of robust fractional-order CRONE control with nonlinear reset is given for both first and second generation CRONE control. General design rules are derived and presented for these CRONE reset controllers. Within this framework, fractional-order control allows for better tuning of the open-loop responses on the one hand. On the other hand, reset control enables a reduction in phase lag and a corresponding increase in phase margin compared to linear control for similar open-loop gain profile. Hence, the combination of the two control methods can provide well-tuned open-loop responses that can overcome the fundamental linear control limitation of Bode's gain-phase relationship. Moreover, as established loop-shaping concepts are used in the controller design, CRONE reset can be highly compatible with the industry. The designed CRONE reset controllers are validated on a one degree-of-freedom Lorentz-actuated precision positioning stage. On this setup, CRONE reset control is shown to provide better tracking performance compared to linear CRONE control, which is in agreement with the predicted performance improvement.Accepted Author ManuscriptMechatronic Systems Desig
Proposed solutions for quantization induced performance deterioration in reset controllers
No full textThe most widely applied feedback controller is PID. This controller gains its popularity because of the ease of design through loop shaping, since PID can be analyzed in the frequency domain. However, PID is limited by linearity. Reset control is a nonlinear addition to PID control. Through linearization techniques it can be designed by analyzing the frequency domain. Through numerous numerical, analytical and practical experiments it has been shown that reset control can outperformPID. However, when practically implementing reset control, especially in motion stages, one aspect can cause severe performance degradation. Research is underrepresented in this field. Quantization can be described as discretization in the amplitude. This thesis aims to reduce the quantization induced performance degradation. Two methods are proposed: reset band and time regularization. Numerical analysis and practical experiments have been performed in order to analyze the performance degradation and proposed methods. Through the numerical analysis in matlab simulink of a mass system the performance degradation has clearly been addressed. Based on the new understanding tuning rules have been provided for both proposed methods. A preliminary sensitivity analysis shows the robustness of both methods. Both proposed methods show enhanced performance. In numerical analysis it was shown that the reset band solution and time regularization can achieve an improvement of up to 10 dB. It was shown through experiments on a high level motion stage that several dB improvement is feasible. For the reset band at a specifically detrimental frequency the error was reduced from 200 nm to 70 nm. The reset band shows an improvement of several dB. In one setup, the performance enhancement spanned a wide frequency range. Overall it is concluded that for quantization induced performance degradation both proposed methods clearly show improvement. Two novel applications of existing methods have shown an increase in performance. New tuning guidelines have been provided.CLOCMechanical Engineering | Mechatronic System Design (MSD
Multimode damping with activated metamaterials: Hexagonal patterned flexure with integrated piezo elements for active damping
No full textHigh Tech industry is looking to push the bounds of what is possible, this requires machines that run with ever increasing speed and precision for longer amount of time under progressively more hostile environments. These requirements necessitate the use of compliant mechanisms/flexures instead of traditional rigid body counterparts. However, as these flexures are pushed to operate at ever higher speeds, high frequency modes affect precision and hence require better damping. Currently active damping relies on a single or small amount of actuators which makes their placement for multimode damping inefficient. To this end, the MetaMech project was created which aims to combine the disciplines of mechatronics and metamaterials to create flexures with integrated cells housing sensors, active and passive dampers in optimal positions and orientations. This will enable more efficient placement and orientation of dampers, reducing the force and thus the size and weight needed to damp the system. This thesis takes the first step in this direction and is concerned with developing the first prototype demonstrator of a metamaterial flexure with integrated damping using currently available technology. The presentation will cover the design, Finite Element Analysis and practical tests of a hexagonal patterned metamaterial flexure with integrated piezo patches. It also presents the design and finite element analysis of a more advanced hexagonal cell able to exert force in three different directions. The results provide proof of concept for the MetaMech project with insights for future work.MetamechMechanical Engineering | Mechatronic System Design (MSD
High Bandwidth Stable Motion Control of Fourth and Higher Order Systems
No full textPID is the most commonly used technique in industrial motion control. It consists of three components - lead, lag and low pass filter (LPF). PID, being a linear control method is inherently bounded by waterbed effect due to which there exists a trade-off between precision, tracking, and stability. Reset control is a nonlinear technique which shows promise in overcoming certain limitations. Despite the promise shown, the use of reset elements other than integrator within the framework of PID for improved performance has not been well investigated. This thesis work focuses on implementing reset in lead part and in LPF in order to reduce the severity of the waterbed effect in PID. Three controllers have been developed that provide improvements in bandwidth, precision, and tracking. The controllers were implemented in a Lorentz-actuated nanometer precision stage and the performance has been validated in both time and frequency domain
Novel Designs to Improve Support Stiffness during Large Strokes in Compliant Mechanism
No full textThe precision, speed, and stroke of mechatronic machines need continuous improvement. Compliant mechanisms are widely used in the precision machines, but they do not have larger strokes due to their limited deformation. In the present time, various applications also require high speed and more problems appear due to the dynamics of the compliant mechanisms. These problems can be solved by improving the support stiffness. In this thesis, novel designs are introduced which improve the support stiffness of 1 DOF translational motion. A novel method is introduced to amplify the strokes and implemented in the proposed designs. This method can be used along with designs that passively maintain the support stiffness, but active approaches are explored. The first active approach is distributed mechatronics and the second approach is an XY stage.The XY stage moves in X- or Y- direction using differential drive. It does not have the first non-collocated mode which is present in existing XY stages having parallel configuration. It also has high yaw rotation stiffness which is verified using experiments. There is no undesired mode occurring within the 9 to 10 times of the desired X-direction mode. In conclusion, the XY stage can be used in industries demanding higher precision and throughput. Further, it opens up the avenue of designing other DOF, more collocated motion stages
Augmented fractional-order reset control: Application in precision mechatronics
No full textLinear control such as PID possesses fundamental limitations, seen through the Waterbed effect. Reset control has been found to be able to overcome these limitations, while still maintaining the simplicity and ease of use of PID control due to its compatibility with the loop shaping method. However, the resetting action also gives rise to higher order harmonics that hinders consistent realization of the aforementioned expected improvement. In this paper, a fractional-order augmented state analogue of the reset integrator is investigated. This analogue is composed of a series of augmented states that each possesses unique reset values, providing the same first order harmonic behavior but reduced higher order harmonics magnitude compared to the reset integrator. The optimal number of augmented states along with the corresponding tuning values are investigated. To validate the improvement, the reset integrator and the optimal fractional order analogue are tuned to equally improve disturbance rejection of a high precision 1 DOF positioning stage while maintaining the stability level, with both designed to overcome linear control. From simulation and experimental results, it was found that the novel fractional-order augmented state analogue gives rise to disturbance rejection performance that is closer to the desired and expected improvement, compared to using the traditional reset integrator.Accepted Author ManuscriptMechatronic Systems Desig
Stability analysis and efficiency of EMPC for Type-1 systems
No full textExperience mapping based predictive controller (EMPC) is a recently developed controller based on the concepts of Human Motor Control. It has been demonstrated to out-perform other classical controllers like proportional-derivative (PD), model reference based adaptive controller (MRAC), linear quadratic regulator (LQR) and the linear quadratic Gaussian (LQG) for both Type-1 and Type-0 systems. This paper analyses the stability and efficiency of EMPC for Type 1 systems. EMPC uses rectangular pulse input as control action for well-damped Type 1 systems and a first order decay input for under-damped Type 1 systems. The simulation results of EMPC for position control of a DC motor with a load coupled through a flexible shaft are presented as a case study to derive and prove the stability criterion. The efficiency of EMPC on a practical system is analysed in terms of energy dissipated in the armature resistance of the motor and the same is compared with PD, MRAC, LQR, LQG controller. Further, the computational cost of EMPC is discussed and compared with traditional controllers from the point of view of implementation.Accepted Author ManuscriptMechatronic Systems Desig
