Chatter mitigation in milling process using discrete time sliding mode control with type 2-fuzzy logic system

In order to achieve a high-quality machining process with superior productivity, it is very important to tackle the phenomenon of chatter in an effective manner. The problems like tool wear and improper surface finish affect the milling process and are caused by self-induced vibration termed as chatter. A strategy to control chatter vibration actively in the milling process is presented. The mathematical modeling of the process is carried out initially. In this paper, an innovative technique of discrete time sliding mode control (DSMC) is blended with the type-2 fuzzy logic system. The proposed active controller results in a significantly high mitigation of vibration. The DSMC is linked to the time-varying gain which is an innovative approach to mitigate chattering. The theorem is laid down which validates that the system states are bounded in the case of DSMC-type-2 fuzzy. Stability analysis is carried out using Lyapunov candidate. The nonlinearities linked with the cutting forces and damper friction are handled effectively by using the type-2 fuzzy logic system. The performance of the DSMC-type-2 fuzzy concept is compared with the discrete time PID (D-PID) and discrete time sliding mode control for validating the effectiveness of the controller. The better performance of DSMC-type-2 fuzzy over D-PID and DSMC-T1 fuzzy in the minimization of milling chatter are validated by a numerical analysis approach

Competency Based Education – Current Global Practices

[EN] Competency Based Education (CBE) is considered an alternative to face the lack of individuals with the appropriate labour abilities. A state of the art on CBE in terms of the practices being performed by main worldwide universities/colleges is presented. Main promoted competencies include effective communication, critical thinking and lifelong learning. Also, teaching and practice activities are determined such as real life situations and simulations. Regarding competency assessment techniques, a mix of them is used to guarantee the desired competency level. Achievements of competencies are reported with a pass or not pass grade and with narrative transcripts. CBE benefits from student's perspective are also determined. The main advantage of CBE is that measures what a student can do after completing a program. It is also flexible, as universities/colleges of any size/age can incorporate it at different levels, which depends on their resources and strategies. Even though CBE has proven to solve a global problem, the gap between the supply and demand of skillful people can only be reduced if all the concerned parties work together in a coordinated manner.Hernández-De-Menéndez, M.; Morales-Menendez, R. (2017). Competency Based Education – Current Global Practices. En Proceedings of the 3rd International Conference on Higher Education Advances. Editorial Universitat Politècnica de València. 1156-1163. https://doi.org/10.4995/HEAD17.2017.55361156116

MRAC + H∞ fault tolerant control for linear parameter varying systems

Presentado al SysTol 2010 celebrado en Niza del 6 al 8 de octubre.Two different schemes for Fault Tolerant Control (FTC) based on Adaptive Control, Robust Control and Linear Parameter Varying (LPV) systems are proposed. These schemes include a Model Reference Adaptive Controller for an LPV system (MRAC-LPV) and a Model Reference Adaptive Controller with a H¿ Gain Scheduling Controller for an LPV system (MRAC-H¿ GS-LPV). In order to compare the performance of these schemes, a Coupled-Tank system was used as testbed in which two different types of faults (abrupt and gradual) with different magnitudes and different operating points were simulated. Results showed that the use of a Robust Controller in combination with an Adaptive Controller for an LPV system improves the FTC schemes because this controller was Fault Tolerant against sensor fault and had an accommodation threshold for actuator fault magnitudes from 0 to 6Peer Reviewe

Fault Estimation Methods for Semi-Active Suspension Systems

International audienceSemi-Active (SA) suspension systems aim to improve the stability and comfort of vehicles. Although they offer better performance than passive suspensions, the actuators such as magneto-rheological dampers are more susceptible to failure. Oil leakage is the most common fault, and its effect is a reduction of the damping force. The estimation of suspension faults can be used with a Fault Tolerant Control system to prevent handling and comfort deterioration. However, fault estimation schemes introduce additional challenges due to the damper non-linear dynamics and the strong influence of the disturbances (i.e the road profile). One of the first obstacles for appropriate damper fault detection is the modeling of the fault, which has been shown to be of multiplicative nature. However, many of the most widespread fault detection schemes consider additive faults due to mathematical convenience. Two complementary model-based fault estimation schemes for semi-active dampers are proposed: an observer-based approach, which is intended to estimate additive faults; and a parameter identification approach, which is intended to estimate multiplicative faults. The performance of these schemes is validated and compared through simulations using a pickup truck model. Early results shows that a parameter identification approach is more accurate in fault estimation, whereas an observer-based approach is less sensible to parametric uncertainty

Chassis Control based on Fuzzy Logic

International audienceBased on a Global Chassis Control system with three-layers architecture (decision, control, and physical layers) a Fuzzy Logic (FL) approach is exploited. The FL based decision layer identifies the current driving condition of the vehicle and decides the control strategy to take care of this driving condition. A confusion matrix validates the classification results. The control strategy is implemented through the subsystems (suspension, steering, and braking) at the FL based control layer. The strategy was evaluated under two different tests: slalom and double line change by comparing the performance with an UnControlled system. Early results show the proposed strategy has less roll, yaw movement and side slip angle than an UnControlled system during a double line change maneuver; also, for the slalom test the proposal improves the dynamic vehicle performance allowing the driver to maintain the vehicle under control

Global Chassis Control System Using Suspension, Steering, and Braking Subsystems

A novel Global Chassis Control (GCC) system based on a multilayer architecture with three levels: top: decision layer, middle: control layer, and bottom: system layer is presented. The main contribution of this work is the development of a data-based classification and coordination algorithm, into a single control problem. Based on a clustering technique, the decision layer classifies the current driving condition. Afterwards, heuristic rules are used to coordinate the performance of the considered vehicle subsystems (suspension, steering, and braking) using local controllers hosted in the control layer. The control allocation system uses fuzzy logic controllers. The performance of the proposed GCC system was evaluated under different standard tests. Simulation results illustrate the effectiveness of the proposed system compared to an uncontrolled vehicle and a vehicle with a noncoordinated control. The proposed system decreases by 14% the braking distance in the hard braking test with respect to the uncontrolled vehicle, the roll and yaw movements are reduced by 10% and 12%, respectively, in the Double Line Change test, and the oscillations caused by load transfer are reduced by 7% in a cornering situation

Fault Tolerant Strategy for Semi-Active Suspensions with LPV Accommodation

International audienceAbstract--A novel fault tolerant strategy to compensate multiplicative actuator faults (damper oil leakages) in a semiactive suspension system is proposed. The compensation of the lack of damping force caused by a faulty damper is carried on by the remainder three healthy semi-active dampers. Once a faulty damper is detected and isolated by a Fault Detection and Isolation strategy based on parity-space, an estimator is activated to compute the missing damping force to compensate. In order to fulfill the semi-active damper constraints, the fault accommodation is based on the Linear-Parameter Varying (LPV) control strategy. Thus, each corner has a fault estimator and an LPV controller oriented to comfort and road holding. Simulation results show that the proposed fault tolerant semiactive suspension improves the vehicle comfort up to 60% with respect to a controlled suspension without fault-tolerant strategy and 82% with respect to a passive suspension

Fault Detection for Automotive Shock Absorber

Fault detection for automotive semi-active shock absorbers is a challenge due to the non-linear dynamics and the strong influence of the disturbances such as the road profile. First obstacle for this task, is the modeling of the fault, which has been shown to be of multiplicative nature. Many of the most widespread fault detection schemes consider additive faults. Two model-based fault algorithms for semiactive shock absorber are compared: an observer-based approach and a parameter identification approach. The performance of these schemes is validated and compared using a commercial vehicle model that was experimentally validated. Early results shows that a parameter identification approach is more accurate, whereas an observer-based approach is less sensible to parametric uncertainty

Adaptive Road Profile Estimation in Semi-Active Car Suspensions

International audienceThe enhancement of the passengers comfort and their safety are part of the constant concerns for car manufacturers. As a solution, the semi-active damping control systems have emerged to adapt the suspension features, where the road profile is one of the most important factors that determine the automotive vehicle performance. Because direct measurements of the road condition represent expensive solutions and, are susceptible to be contaminated, this paper proposes a novel road profile estimator that offers the essential information (road roughness and its frequency) for the adjustment of the vehicle dynamics by using conventional sensors of cars. Based on the Q-parametrization approach, an adaptive observer estimates the dynamic road signal, posteriorly, a Fourier analysis is used to compute online the road roughness condition and perform an ISO 8608 classification. Experimental results on the rear-left corner of a 1:5 scale vehicle, equipped with Electro-Rheological (ER) dampers, have been used to validate the proposed road profile estimation method. Different ISO road classes evaluate online the performance of the road identification algorithm, whose results show that any road can be identified successfully at least 70% with a false alarm rate lower than 5%; the general accuracy of the road classifier is 95%. A second test with variable vehicle velocity shows the importance of the online frequency estimation to adapt the road estimation algorithm to any driving velocity, in this test the road is correctly estimated 868 of 1,042 m (error of 16.7%). Finally, the adaptability of the parametric road estimator to the semi-activeness property of the ER damper is tested at different damping coefficients

Fault Tolerant Control with Additive Compensation for Faults in an Automotive Damper

International audienceAbstract--A novel Fault-Tolerant Controller is proposed for an automotive suspension system based on a Quarter of Vehicle (QoV) model. The design is divided in a robust Linear Parameter-Varying controller used to isolate vibrations from external disturbances and in a compensation mechanism used to accommodate actuator faults. The compensation mechanism is based on a robust fault detection and estimation scheme that reconstructs a fault on the semi-active damper; this information is used to reduce the failure effect into the vertical dynamics to achieve good control performances. Validations have been made over a QoV model in CarSimTM. Results show the effectiveness of the faulttolerant semi-active damper versus an uncontrolled damper; the improvement is 50.4% in comfort and 42.4% in road holding, by avoiding biases in the damper deflection