Fargham Sandhu | Federal Urdu University of Arts, Science and Technology,Islamabad, Pakistan (original) (raw)
Papers by Fargham Sandhu
EMITTER International Journal of Engineering Technology, 2021
The growing demands for mobile broadband application services along with the scarcity of the spec... more The growing demands for mobile broadband application services along with the scarcity of the spectrum have triggered the dense utilization of frequency resources in cellular networks. The capacity demands are coped accordingly, however at the detriment of added inter-cell interference (ICI). Fractional Frequency Reuse (FFR) is an effective ICI mitigation approach when adopted in realistic irregular geometry cellular networks. However, in the literature optimized spectrum resources for the individual users are not considered. In this paper Hungarian Mechanism based Sectored Fractional Frequency Reuse (HMS-FFR) scheme is proposed, where the sub-carriers present in the dynamically partitioned spectrum are optimally allocated to each user. Simulation results revealed that the proposed HMS-FFR scheme enhances the system performance in terms of achievable throughput, average sum rate, and achievable throughput with respect to load while considering full traffic.
Jurnal Teknologi, 2015
Antilock braking systems use slip to control braking, for which the velocity of the car and wheel... more Antilock braking systems use slip to control braking, for which the velocity of the car and wheel speeds of the wheels are required. The wheel speeds can be measured directly but the velocity of the vehicle is difficult to measure. Although the wheel speed can be used to calculate the linear velocity of the vehicle using the tire characteristic function, it depends upon various environmental and time varying parameters. The dominant factor in the characteristic function is the road friction coefficient. Due to the difficulties in proper estimation of the road friction, most systems calculate the optimal values offline and apply them at different speeds using switching functions. By using the tire model and the optimal friction coefficients, the velocity of the vehicle is estimated and used for calculating the optimal braking force, resulting in inappropriate control of braking creating longer braking distances. In the method proposed in this paper, an estimator will be used to estim...
Modern vehicle stability and navigational systems are mostly designed using inaccurate bicycle mo... more Modern vehicle stability and navigational systems are mostly designed using inaccurate bicycle models to approximate the full-car models. This results in incomplete models with various unknown parameters and states being neglected in the controller and navigation system design processes. Earlier estimation algorithms using the bicycle models are simpler but have many undefined parameters and states that are crucial for proper stability control. For existing vehicle navigation systems, direct line of sight for satellite access is required but is limited in modern cities with many high-rise buildings and therefore, an inertial navigation system utilizing accurate estimation of these parameters is needed. The aim of this research is to estimate the parameters and states of the vehicle more accurately using a multivariable and complex full-car model. This will enhance the stability of the vehicle and can provide a more consistent navigation. The proposed method uses the kinematics estim...
Earlier models were a simplified form of the complex vehicle system, which was governed by the im... more Earlier models were a simplified form of the complex vehicle system, which was governed by the important parameters and states. These parameters and states were either obtained indirectly through some simplified equations or directly measured using instrumentation. In either case, the models were designed on the basis of parameters and state availability or importance, and not to have a complete model representation and maximum parameter utilization through estimation and instrumentation. Since a complete vehicle model can lead to a better controller. Without considering all the important parameters, a complete model is not obtained to design better controllers. All types of controllers, classical, optimal, nonlinear and linear controllers use the basic equations that govern the vehicle dynamics. This paper reviews all the previous models with greater insight into each system. The aim is to provide a better understanding of each model, its shortcomings and how it can represent the c...
TELKOMNIKA (Telecommunication Computing Electronics and Control)
Irrational crowds tend to adapt herd mentality, having group behaviour and high suggestion throug... more Irrational crowds tend to adapt herd mentality, having group behaviour and high suggestion through interaction. It is important to see how an irrational crowd can be controlled to prevent undesirable crowd attitude. This paper reviews existing models and the controllers to provide a comprehensive study for crowd control. It focuses on a comprehensive analysis of the control of psychological crowd, modelled using LeBon's theory; which defines the crowd behaviour in terms of crowd attitude. The crowd attitude is defined in terms of suggestibility and prestige and the crowd interaction is defined in terms of the interaction of prestige and suggestibility, which is naturally unstable. A controller is required to achieve stability. In this paper several control approaches are described and the best control approach is highlighted. The results conclude, the best control approach is using multiple control agents, since the control effort is reduced and the stabilizing time is improved.
Advances in Electrical and Computer Engineering
1 Abstract—Direct yaw control of four-wheel vehicles using optimal controllers such as the linear... more 1 Abstract—Direct yaw control of four-wheel vehicles using optimal controllers such as the linear quadratic regulator (LQR) and the sliding mode controller (SMC) either considers only certain parameters constant in the nonlinear equations of vehicle model or totally neglect their effects to obtain simplified models, resulting in loss of states for the system. In this paper, a modified state-dependent Ricatti equation method obtained by the simplification of the vehicle model is proposed. This method overcomes the problem of the lost states by including state integrals. The results of the proposed system are compared with the sliding mode slip controller and state-dependent Ricatti equation method using high fidelity vehicle model in the vehicle simulation software package, Carsim. Results show 38% reduction in the lateral velocity, 34% reduction in roll and 16% reduction in excessive yaw by only increasing the fuel consumption by 6.07%.
Jurnal Teknologi, 2016
The behavior of human crowd is an interesting phenomenon in which individuals are set as a collec... more The behavior of human crowd is an interesting phenomenon in which individuals are set as a collection that comprises of a highly dynamic social group. The crowd behaviors have been investigated by researchers over the years. Recent works include the study in modeling and controlling of the dynamic psychological behavior of crowds such as students' behavior in a classroom or people's behavior in a one-dimensional queue. In this paper, an improved version of the psychological crowd model has been proposed, where the social interaction between two individuals in a crowd is represented by a weightage, called the weight of social interaction. It has been shown that the inclusion of the social interaction weight has allowed social interactions between individuals to be included and results in a more accurate representation of the crowd's psychological factors propagations. Since the psychological dynamics of crowd is naturally unstable, this paper also discusses the application of two nonlinear control approaches to stabilise the crowd to make it calm. Results show that for a crowd of n number of agents, the single-agent controller gives similar performance with the n-agent controller but with much less resources. The simulation results also show that it takes less amount of time to stabilise a crowd when the crowd model includes social interaction weights.
Applied Mechanics and Materials, Nov 26, 2014
The use of Inertial Navigational System (INS) has been proven to be suitable for vehicular stabil... more The use of Inertial Navigational System (INS) has been proven to be suitable for vehicular stability and control. The same system can be used for inertial based navigation in the absence of GPS. In this paper, the problem of obtaining good attitude estimates from low cost sensors used for car navigation in the absence of GPS data is discussed. The states to be estimated are using angular velocity and linear accleration signals obtained from the sets of gyros and accelerometers of the INS. The special orthogonal group, the SO(3)-based complementary filters, have been used as the estimators as they are most suited for embedded systems to generate highly efficient algorithms for navigation. The INS has also been integrated with a set of magnetometers to assist in achieving global navigation. This integration requires kinematics equations as well as the inclusion of the gyro and accelerometer calibration and filtering. By using the quatronion representation, not only highly compact algorithms for integration can be generated, but it can also estimate and remove the effects of other biases and misalignments caused by, for instance, inaccurate installations and inherent sensors problems. The results obtained through simulation indicate better performance then Kalman filter approach as well as iterative recursive least square approach even with low grade sensors. The results are comparable with attitude estimation using roll index but with much less computations and better performance.
2015 10th Asian Control Conference (ASCC), 2015
Psychological dynamics that are created by the interactions among persons within One-Dimensional ... more Psychological dynamics that are created by the interactions among persons within One-Dimensional Queue, specially the spread of actions from person to person is discussed in this paper. The instability of psychological dynamic factors can be overcome by persons' interactions in a crowd dynamic. Surowiecki's theory states that the individuals in a crowd are not affected by each other in terms of attitudes. This state indicates wisdom of crowd while Gustav Le Bon's theory is in contrast with. The purpose of this paper is to prove that Surowiecki's theory is originated from Gustav Le Bon's theory if there is a large distance between the members of group in the one dimensional queue. This paper proposes a dynamic crowd model by Bergey, Spieser and Davison based on Gustav Le Bon's theory for static crowd model with variable distance interaction; resulting into better control of crowd dynamics using distance interaction.
2015 10th Asian Control Conference (ASCC), 2015
The use of magnetorheological (MR) dampers on a semiactive vehicle suspension system results in a... more The use of magnetorheological (MR) dampers on a semiactive vehicle suspension system results in a less satisfactory performance than fully-active suspensions due to the limited input range and approximate controllers for MR damper-based suspension system. Many existing schemes for MR damper control use linear quadratic recursive methods to optimize the control input without considering the full car model and the MR damper characteristics. Skyhook control scheme has shown good performance in quarter car models than the optimized linear quadratic recursive controllers but has not been used very much in conjunction with a full car model. In this paper, by designing a controller that incorporates the skyhook control with an optimized linear quadratic control scheme based on a full car model, the MR dampers can improve the ride comfort by reducing the displacement of the chassis with reduced steady-state time required for vibration damping. This is because, the full car model does not only consider the motion of the chassis along the vertical direction, but also the attitude disturbances in the suspension system controller design. The significance of considering the attitude disturbances is that the suspension can efficiently damp the disturbances coupled by the four wheels to reduce its effects at the center of gravity. The cost function used constitutes the energy of the suspension and the disturbance input. By optimizing the cost function, the total energy is restrained to the minimization of the suspension energy resulting into a more comfortable ride. The cost function is used as a yard stick to evaluate the ride comfort of the system. A centralized controller complements the need for a controller for each damper with improvement in system dynamics.
EMITTER International Journal of Engineering Technology, 2021
The growing demands for mobile broadband application services along with the scarcity of the spec... more The growing demands for mobile broadband application services along with the scarcity of the spectrum have triggered the dense utilization of frequency resources in cellular networks. The capacity demands are coped accordingly, however at the detriment of added inter-cell interference (ICI). Fractional Frequency Reuse (FFR) is an effective ICI mitigation approach when adopted in realistic irregular geometry cellular networks. However, in the literature optimized spectrum resources for the individual users are not considered. In this paper Hungarian Mechanism based Sectored Fractional Frequency Reuse (HMS-FFR) scheme is proposed, where the sub-carriers present in the dynamically partitioned spectrum are optimally allocated to each user. Simulation results revealed that the proposed HMS-FFR scheme enhances the system performance in terms of achievable throughput, average sum rate, and achievable throughput with respect to load while considering full traffic.
Jurnal Teknologi, 2015
Antilock braking systems use slip to control braking, for which the velocity of the car and wheel... more Antilock braking systems use slip to control braking, for which the velocity of the car and wheel speeds of the wheels are required. The wheel speeds can be measured directly but the velocity of the vehicle is difficult to measure. Although the wheel speed can be used to calculate the linear velocity of the vehicle using the tire characteristic function, it depends upon various environmental and time varying parameters. The dominant factor in the characteristic function is the road friction coefficient. Due to the difficulties in proper estimation of the road friction, most systems calculate the optimal values offline and apply them at different speeds using switching functions. By using the tire model and the optimal friction coefficients, the velocity of the vehicle is estimated and used for calculating the optimal braking force, resulting in inappropriate control of braking creating longer braking distances. In the method proposed in this paper, an estimator will be used to estim...
Modern vehicle stability and navigational systems are mostly designed using inaccurate bicycle mo... more Modern vehicle stability and navigational systems are mostly designed using inaccurate bicycle models to approximate the full-car models. This results in incomplete models with various unknown parameters and states being neglected in the controller and navigation system design processes. Earlier estimation algorithms using the bicycle models are simpler but have many undefined parameters and states that are crucial for proper stability control. For existing vehicle navigation systems, direct line of sight for satellite access is required but is limited in modern cities with many high-rise buildings and therefore, an inertial navigation system utilizing accurate estimation of these parameters is needed. The aim of this research is to estimate the parameters and states of the vehicle more accurately using a multivariable and complex full-car model. This will enhance the stability of the vehicle and can provide a more consistent navigation. The proposed method uses the kinematics estim...
Earlier models were a simplified form of the complex vehicle system, which was governed by the im... more Earlier models were a simplified form of the complex vehicle system, which was governed by the important parameters and states. These parameters and states were either obtained indirectly through some simplified equations or directly measured using instrumentation. In either case, the models were designed on the basis of parameters and state availability or importance, and not to have a complete model representation and maximum parameter utilization through estimation and instrumentation. Since a complete vehicle model can lead to a better controller. Without considering all the important parameters, a complete model is not obtained to design better controllers. All types of controllers, classical, optimal, nonlinear and linear controllers use the basic equations that govern the vehicle dynamics. This paper reviews all the previous models with greater insight into each system. The aim is to provide a better understanding of each model, its shortcomings and how it can represent the c...
TELKOMNIKA (Telecommunication Computing Electronics and Control)
Irrational crowds tend to adapt herd mentality, having group behaviour and high suggestion throug... more Irrational crowds tend to adapt herd mentality, having group behaviour and high suggestion through interaction. It is important to see how an irrational crowd can be controlled to prevent undesirable crowd attitude. This paper reviews existing models and the controllers to provide a comprehensive study for crowd control. It focuses on a comprehensive analysis of the control of psychological crowd, modelled using LeBon's theory; which defines the crowd behaviour in terms of crowd attitude. The crowd attitude is defined in terms of suggestibility and prestige and the crowd interaction is defined in terms of the interaction of prestige and suggestibility, which is naturally unstable. A controller is required to achieve stability. In this paper several control approaches are described and the best control approach is highlighted. The results conclude, the best control approach is using multiple control agents, since the control effort is reduced and the stabilizing time is improved.
Advances in Electrical and Computer Engineering
1 Abstract—Direct yaw control of four-wheel vehicles using optimal controllers such as the linear... more 1 Abstract—Direct yaw control of four-wheel vehicles using optimal controllers such as the linear quadratic regulator (LQR) and the sliding mode controller (SMC) either considers only certain parameters constant in the nonlinear equations of vehicle model or totally neglect their effects to obtain simplified models, resulting in loss of states for the system. In this paper, a modified state-dependent Ricatti equation method obtained by the simplification of the vehicle model is proposed. This method overcomes the problem of the lost states by including state integrals. The results of the proposed system are compared with the sliding mode slip controller and state-dependent Ricatti equation method using high fidelity vehicle model in the vehicle simulation software package, Carsim. Results show 38% reduction in the lateral velocity, 34% reduction in roll and 16% reduction in excessive yaw by only increasing the fuel consumption by 6.07%.
Jurnal Teknologi, 2016
The behavior of human crowd is an interesting phenomenon in which individuals are set as a collec... more The behavior of human crowd is an interesting phenomenon in which individuals are set as a collection that comprises of a highly dynamic social group. The crowd behaviors have been investigated by researchers over the years. Recent works include the study in modeling and controlling of the dynamic psychological behavior of crowds such as students' behavior in a classroom or people's behavior in a one-dimensional queue. In this paper, an improved version of the psychological crowd model has been proposed, where the social interaction between two individuals in a crowd is represented by a weightage, called the weight of social interaction. It has been shown that the inclusion of the social interaction weight has allowed social interactions between individuals to be included and results in a more accurate representation of the crowd's psychological factors propagations. Since the psychological dynamics of crowd is naturally unstable, this paper also discusses the application of two nonlinear control approaches to stabilise the crowd to make it calm. Results show that for a crowd of n number of agents, the single-agent controller gives similar performance with the n-agent controller but with much less resources. The simulation results also show that it takes less amount of time to stabilise a crowd when the crowd model includes social interaction weights.
Applied Mechanics and Materials, Nov 26, 2014
The use of Inertial Navigational System (INS) has been proven to be suitable for vehicular stabil... more The use of Inertial Navigational System (INS) has been proven to be suitable for vehicular stability and control. The same system can be used for inertial based navigation in the absence of GPS. In this paper, the problem of obtaining good attitude estimates from low cost sensors used for car navigation in the absence of GPS data is discussed. The states to be estimated are using angular velocity and linear accleration signals obtained from the sets of gyros and accelerometers of the INS. The special orthogonal group, the SO(3)-based complementary filters, have been used as the estimators as they are most suited for embedded systems to generate highly efficient algorithms for navigation. The INS has also been integrated with a set of magnetometers to assist in achieving global navigation. This integration requires kinematics equations as well as the inclusion of the gyro and accelerometer calibration and filtering. By using the quatronion representation, not only highly compact algorithms for integration can be generated, but it can also estimate and remove the effects of other biases and misalignments caused by, for instance, inaccurate installations and inherent sensors problems. The results obtained through simulation indicate better performance then Kalman filter approach as well as iterative recursive least square approach even with low grade sensors. The results are comparable with attitude estimation using roll index but with much less computations and better performance.
2015 10th Asian Control Conference (ASCC), 2015
Psychological dynamics that are created by the interactions among persons within One-Dimensional ... more Psychological dynamics that are created by the interactions among persons within One-Dimensional Queue, specially the spread of actions from person to person is discussed in this paper. The instability of psychological dynamic factors can be overcome by persons' interactions in a crowd dynamic. Surowiecki's theory states that the individuals in a crowd are not affected by each other in terms of attitudes. This state indicates wisdom of crowd while Gustav Le Bon's theory is in contrast with. The purpose of this paper is to prove that Surowiecki's theory is originated from Gustav Le Bon's theory if there is a large distance between the members of group in the one dimensional queue. This paper proposes a dynamic crowd model by Bergey, Spieser and Davison based on Gustav Le Bon's theory for static crowd model with variable distance interaction; resulting into better control of crowd dynamics using distance interaction.
2015 10th Asian Control Conference (ASCC), 2015
The use of magnetorheological (MR) dampers on a semiactive vehicle suspension system results in a... more The use of magnetorheological (MR) dampers on a semiactive vehicle suspension system results in a less satisfactory performance than fully-active suspensions due to the limited input range and approximate controllers for MR damper-based suspension system. Many existing schemes for MR damper control use linear quadratic recursive methods to optimize the control input without considering the full car model and the MR damper characteristics. Skyhook control scheme has shown good performance in quarter car models than the optimized linear quadratic recursive controllers but has not been used very much in conjunction with a full car model. In this paper, by designing a controller that incorporates the skyhook control with an optimized linear quadratic control scheme based on a full car model, the MR dampers can improve the ride comfort by reducing the displacement of the chassis with reduced steady-state time required for vibration damping. This is because, the full car model does not only consider the motion of the chassis along the vertical direction, but also the attitude disturbances in the suspension system controller design. The significance of considering the attitude disturbances is that the suspension can efficiently damp the disturbances coupled by the four wheels to reduce its effects at the center of gravity. The cost function used constitutes the energy of the suspension and the disturbance input. By optimizing the cost function, the total energy is restrained to the minimization of the suspension energy resulting into a more comfortable ride. The cost function is used as a yard stick to evaluate the ride comfort of the system. A centralized controller complements the need for a controller for each damper with improvement in system dynamics.