Amir Khajepour's research while affiliated with University of Waterloo and other places
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Publications (591)
The air suspension uses a combination of flexible air springs to transfer the chassis load to the axles.
The vehicle suspension system aims to provide a comfortable ride and stable handling. However, these two objectives are conflicting, so the conventional passive suspension design has to compromise between ride comfort and handling stability.
Suspension geometry plays an important role in wheel angles and movements, all of which affect vehicle road holding, handling, and safety.
To many focusing on ride comfort, it may seem like the suspension system is merely a set of springs and shock absorbers that connect the wheels to the vehicle body. However, this is a very simplistic viewpoint of the suspension system.
A solid axle is known to be the first suspension type used in vehicles where the wheels are mounted at either ends of a rigid beam.
Truck manufacturers place more emphasis on drivers’ health, safety, and comfort in recent decades. Some progresses have been made in reducing drivers’ vibration exposure levels by adding semi-active cabin suspension systems. Considering various driving conditions of a commercial vehicle, an advanced cabin suspension control needs to be capable of s...
This book encompasses all essential aspects of suspension systems and provides an easy approach to their understanding and design. The book is intended specifically for undergraduate students and is accessible to anyone with an interest in learning about the foundations and design of suspension systems. This book uses a step-by-step approach using...
Predicting object motion behaviour is a challenging but crucial task for safe decision making and path planning for autonomous vehicles. It is challenging in large part due to the uncertain, multi-modal, and practically intractable set of possible agent-agent and agent-space interactions, especially in urban driving settings. Models solely based on...
This paper proposes a novel integrated path following control scheme for a 4-Wheel Independent Drive (4WID) autonomous vehicle that can adaptively change its mechanism according to the driving conditions. The proposed integrated system handles the lateral steering controller, longitudinal speed, and yaw moment controls considering tire force capaci...
Vehicle semi-active suspension systems can provide a satisfactory compromise of ride comfort and handling stability. With the rapid developments of damping control methodologies, ride comfort is expected to be improved in all three directions, i.e., vertical, roll, and pitch. Considering this kind of multi-objective coordinated control problem, Mod...
Various cabin designs have been developed for commercial vehicles to meet different driver comfort requirements. Among those configurations, the cab-over-engine (COE) is widely used because of its compact size and good road visibility. Since the engine is assembled underneath the cabin, it is required that the cabin can be entirely tilted forward i...
To improve the safety and driving stability of the autonomous heavy truck, it is necessary to consider the differences of driving behavior and drivable trajectories between the heavy trucks and passenger cars. This study proposes a probabilistic decision-making and trajectory planning framework for the autonomous heavy trucks. Firstly, the driving...
The present work is the first to show the effect of processing cooling rate on phase structure and the resulting nano-scale deformation mechanisms in functionally graded stainless steels produced by directed energy deposition. To this end, fabrication by laser additive manufacturing involved implementing a closed-loop feedback control approach to m...
This paper proposes a novel prioritisation model predictive control for improving the handling and stability of all-wheel-drive vehicles configured with an electric motor and an open differential per axle with differential braking capability. The configuration of the powertrain provides a significant handling improvement by optimising front/rear to...
Tire states and capacity monitoring is critical for vehicle and wheel stabilization controls in automated driving and active safety systems. Tire capacity, which represents the performance margin of tire forces from its limits, determines the operational range for vehicle control systems and their actuation through steering or torques at each tire...
Predicting object motion behaviour is a challenging but crucial task for safe decision making and path planning for an autonomous vehicle. It is challenging in large part due to the uncertain, multi-modal, and practically intractable set of possible agent-agent and agent-space interactions, especially in urban driving settings. Models solely based...
The tire-road friction coefficient is an important and fundamental parameter in vehicle dynamics. It is a physical limit that vehicles cannot exceed, and it is determined by various factors, such as the road condition and tire material. The friction coefficient is crucial information in vehicle control systems that concerns the safety of passengers...
Herein, various underlying technologies for tire condition monitoring systems (TCMSs) are briefly studied. The technologies that can be implemented in tire systems for sensing and energy harvesting are booming. In this chapter, the mainstream technologies reported to handle the above-mentioned applications are briefly described.
Tire dynamics have been challenging to analyze due to complex characteristics and the fact that it is the only medium of continuous interaction between tires and roads [1]. In recent years, researchers have focused on the intricate mechanisms of tires and dynamic tire-road interactions [2, 3], and several research works have been carried out.
Tire is the only component of a vehicle that makes contact with the road; thus, much important vehicle performance relies on the complex interaction between the tire and road. Tire models are used to describe tire behaviors in terms of mechanical, thermal and wear properties. These models are considered critical in various areas, such as vehicle dy...
Tires are one of the most essential components in vehicle dynamics in terms of safety for drivers and passengers. Accordingly, it is important to develop a tire condition monitoring system (TCMS), such as tire pressure monitoring, to improve road traffic safety and reduce disastrous accidents due to tire failure.
In the research of autonomous vehicles, most existing studies treat the decision/planning and control as two separate problems. This idea originates from robotics. But since there are essential differences between robot and autonomous vehicle, the structure in Robotics may not be suitable for autonomous vehicles. Considering decision/planning and c...
As described in the introduction of tire forces in the previous section, a comprehensive understanding of the tire-road interaction mechanism is essential for vehicle control and safety. In addition to the tire forces, also the slip angle and the slip ratio, which describe the level of tire sliding with respect to the road surface, are valuable for...
Accurate estimation of the tire slip ratio is critical for vehicle safety, as it is necessary for vehicle control purposes. In this paper, an intelligent tire system is presented to develop a novel slip ratio estimation model using machine learning (ML) algorithms. The accelerations, generated by a triaxial accelerometer installed onto the inner li...
This paper presents a prioritization model predictive control for integrated lateral and roll stability control of all-wheel-drive vehicles. The vehicle’s powertrain includes an electric motor and an open differential per axle, which enables generating a corrective yaw moment by front/rear torque shifting. In addition, the brakes can be used in dif...
Vehicle-trailer systems have various unstable modes including trailer snaking, jack-knifing, and roll-over, which should be considered in their stability control. For stability control design purposes, various techniques have been proposed to estimate vehicle-trailer system states and parameters. Some of these techniques rely on vehicle kinematic/d...
Model predictive control (MPC) in automotive active safety applications has gained great success in recent years. Detailed vehicle models along with a receding horizon control scheme seek the optimal control distribution among actuators for enhanced performances while satisfying system constraints. To promote the re-usability and scalability of MPC...
Path following control is a crucial technology for intelligent vehicle, while the control accuracy and the robustness under various road adhesive conditions are two key elements of this technology. However, the accuracy and the robustness are hard to be achieved simultaneously owing to the uncertainties in vehicle dynamics model, especially the per...
Vehicle localization is essential for intelligent and autonomous vehicles. To improve the accuracy of vehicle stand-alone localization in highly dynamic driving conditions during GNSS (Global Navigation Satellites Systems) outages, this paper proposes a vehicle localization system based on vehicle chassis sensors considering vehicle lateral velocit...
Committed to optimizing the fuel economy of hybrid electric vehicles (HEVs), improving the working conditions of the engine, and promoting research on deep reinforcement learning (DRL) in the field of energy management strategies (EMSs), this article first proposed a DRL-based EMS combined with a rule-based engine start–stop strategy. Moreover, con...
A multi-actuation model predictive controller is designed to improve the stability of the performance vehicles during high-speed maneuvers. The actuators included in this study are four electric motors for the wheels and two active aerodynamic wings at the front and rear of the vehicle. The designed controller integrates optimal corner torque alloc...
Among numerous functions performed by the battery management system (BMS), online estimation of the state of health (SOH) is an essential and challenging task to be accomplished periodically. In electric vehicle (EV) applications, accurate SOH estimation minimizes failure risk and improves reliability by predicting battery health conditions. The ch...
In this paper, a new approach in estimating the lateral tire forces and hitch-forces of a vehicle-trailer system is introduced. It is shown that the proposed hitch-force estimation is independent of trailer mass and geometry, by utilizing the vehicle velocity, acceleration, torque engine, wheel's speed, and steering angle measurements. The designed...
Recent advances in artificial intelligence, computer science, communication, sensing and actuation technologies have resulted in the development of several novel intelligent systems. At the same time, the emergence of nanogenerators has opened a new research avenue with the overarching goal of developing self-powered sensing systems. The concepts o...
This paper presents a novel integrated control framework that includes simultaneous vehicle lateral stabilization and path tracking by considering the combined-slip effect, wheel dynamics, and tire force nonlinearities for driver-assistance systems. Active front steering and brakes are the actuators of the developed slip-aware receding horizon cont...
Variable-structure cable-driven parallel robots (VSCR) are a new class of cable robots that are able to cover nonconvex installation spaces by permitting collisions between cables and fixed objects in the environment. In this article, we show how the configuration space of a general planar VSCR can be represented as an organized set of partially ov...
Detecting driver inattentive behaviors is crucial for driving safety in a driver monitoring system (DMS). Recent works treat driver distraction detection as a multiclass action recognition problem or a binary anomaly detection problem. The former approach aims to classify a fixed set of action classes. Although specific distraction classes can be p...
Accurate forecasting of future traffic is a critical contemporary problem for transportation research. However, it is difficult to understand the feature patterns of traffic events due to the complexity of the traffic environment, heterogeneous factors, and lack of abnormal samples. This article proposes a framework to integrate the social traffic...
An autonomous vehicle sideslip angle estimation algorithm is proposed based on consensus and vehicle kinematics/dynamics synthesis. Based on the velocity error measurements between the reduced Inertial Navigation System (R-INS) and the global navigation satellite system (GNSS), a velocity-based Kalman filter is formalized to estimate the velocity e...
This article presents a model predictive control design for improving the yaw stability of a rear-wheel-drive vehicle equipped with an electronic limited slip differential (ELSD) and differential braking capability. It first develops a model for an ELSD system for predicting its torque distribution dynamics, then uses the model in designing an inte...
Understanding the dynamic behavior of tires and their interactions with roads plays an important role in designing integrated vehicle control strategies. Accordingly, having access to reliable information about tire-road interactions through tire-embedded sensors is desirable for developing enhanced vehicle control systems. Thus, the main objective...
A closed-loop laser additive manufacturing (CLAM) system was developed to monitor and control layer-by-layer fabrication via directed energy deposition (DED). The well-modified laser additive manufacturing (LAM) package utilizes a thermal infrared camera and thermal image processing algorithms to extract and control the thermal dynamics of the proc...
This paper proposes two different approaches for estimating grade and bank angles for arbitrary vehicle-trailer configurations independent from road friction conditions: model-based and Machine Learning (ML) approaches. The model-based method employs unknown input observers on a vehicle-trailer roll/pitch dynamic model with fault thresholds. In the...
The rapid development of advanced vehicular mechatronic systems help to bring vehicle performances to a higher level. To fully unleash the power of such systems, an integrated vehicular control framework has been widely adopted. All actuators, along with their impact on vehicle dynamics are considered in a holistic model, and control performances b...
Counterbalancing mechanisms considerably reduce the size of actuators in serial robots. However, by limiting the joints’ angles, imposing dead-point configurations, adding extra links, and attaching heavy/bulky balancing springs/counterweights, they sacrifice the dexterity of serial robots. Such limitations prevent serial robots from being implemen...
This paper investigates the problem of improving vehicle stability using an electronic limited slip differential (ELSD). Unlike brake-based vehicle stability control systems, electronic limited slip differentials have the potential to control a vehicles yaw stability without slowing down its speed. In this study, first, an ELSD model is designed to...
This article presents redundancy resolution and disturbance rejection via torque optimization in hybrid cable-driven robots (HCDRs). To begin with, we present a redundant HCDR for nonlinear whole-body system modeling and model reduction. Based on the reduced dynamic model, two new methods are proposed to solve the redundancy resolution problem: 1)...
This article presents the sensing and safety algorithms for autonomous excavators operating on construction sites. Safety is a key concern for autonomous construction to reduce collisions and machinery damage. Taking this point into consideration, our study deals with LiDAR data processing that allows for object detection, motion tracking/predictio...
Cable-driven parallel robots (CDPR) have seen great advances over the past two decades; however, they remain plagued by their inability to cover non-convex installation-spaces and low workspace to installation-space ratios relative to their rigid counterparts. These fundamental limitations arise because of the need to avoid collisions between cable...
This paper presents a novel vehicle control algorithm for the vehicle following problem. The follower vehicle is tracking the path of the leader while maintaining a velocity-dependent inter-vehicle distance. The follower is equipped with an on-board radar and both vehicles can exchange information via vehicle-to-vehicle (V2V) communication. The pro...
In this paper, ultra-sonic sensors along with kinematics and dynamics equations of a towing vehicle are used to develop three approaches for hitch angle estimation. The first approach is based on direct calculation of hitch angle using certain a priori geometric information and distance measurements of four ultra-sonic sensors. An angle estimate is...
Taking advantage of available measurement in Internet of Things (IoT) for intelligent transportation systems, a sideslip angle estimation method for autonomous vehicles is presented and experimentally verified by fusing global navigation satellite system (GNSS) and inertial measurement unit (IMU), and by constructing an observability index. The cor...
This paper investigates the handling control and stability of an all-wheel-drive vehicle whose axles are individually equipped with an electric motor connected to an open differential. This could offer a potential configuration for the mass production of electric all-wheel-drive vehicles because of reduced cost and complexity. Although there is no...
In order to improve the path following performance of intelligent vehicles while ensure their dynamics stability in extreme
conditions, control and coordination algorisms are designed based on the respective characteristics of steering and direct yaw moment
(DYC) systems for four-wheel drive electric intelligent vehicles. Firstly, for the uncertain...
A novel real-time road bank estimation method is proposed and experimentally verified by using a state-constrained Kalman-based disturbance observer on the combined lateral and roll dynamics of the vehicle. Road-body kinematics, which relates road angle rates and vehicle pitch/roll rates, is also implemented to improve the accuracy of vehicle angle...
This paper develops multiple fixed model blending based adaptive parameter identification schemes for multi-input multi-output (MIMO) systems with polytopic parameter uncertainty. The developed identification schemes are proven to be asymptotically stable for uncertain linear time-invariant (LTI) MIMO systems, and is shown to provide fast adaptatio...
To reduce the driveline oscillations during the shifting process of electric delivery vans (EDVs), this article proposes a swift and smooth disengagement strategy for the clutch in a dual-speed transmission (DST) system. Firstly, a novel electromechanical clutch actuator (ECA) for the proposed DST is designed and modeled. Then the structure of the...
Electric dump trucks are expected to work in fast-changing conditions of torque and speed which causes the inefficient working status of traction motors. To improve the economic performance of the dump truck, a novel integrated dual-motor transmission is proposed in this paper. The energy consumption level of this kind of system relies on a wise en...
A Hydraulic Variable Valve Actuation (HVVA) system is studied in this work, it can continuously adjust engine valve timing and lift at any engine speeds by using a hydraulic actuation system. A detailed co-simulation model is built to reveal relationship between hydraulic pressure, engine valve lift and power consumption, it has taken flow rate, fl...
To improve the economic and comfort performance of pure electric vehicles (PEV), this paper proposes a novel H-infinity gear-shifting controller for dual-speed Transmissions (DST) to achieve a smooth and swift shifting when considering uncertain disturbances in system. Firstly, the structure as well as the working principle of the DST for PEV are i...
This study presents a novel approach in vehicle modeling to provide a unified reconfigurable vehicle dynamics model. The introduced vehicle model is applicable for analysis, design, and control of a wide variety of vehicles and can be reconfigured for four- and three-wheeled vehicles. Active steering, differential braking, torque vectoring, and act...
This paper presents a generic feature-based navigation framework for autonomous vehicles using a soft constrained Particle Filter. Selected map features, such as road and landmark locations, and vehicle states are used for designing soft constraints. After obtaining features of mapped landmarks in instance-based segmented images acquired from a mon...
Excavation is one of the primary projects in the construction industry. Introducing various technologies for full automation of the excavation can be a solution to improve sensing and productivity that are the ongoing issues in this area. This paper covers three aspects of effective excavation progress monitoring that include excavation volume esti...
This paper presents a kinematically constrained planar hybrid cable-driven parallel robot (HCDPR) for warehousing applications as well as other potential applications such as rehabilitation. The proposed HCDPR can harness the strengths and benefits of serial and cable-driven parallel robots. Based on this robotic platform, the goal in this paper is...
This paper aims to address some of the current limitations of cable driven parallel robots (CDPR) by enabling regional changes in dynamic structure through collisions between cables and fixed objects placed in the work area (such as idler pulleys). This leads to the definition of a new class of robots referred to as variable structure cable-driven...
Cable-driven parallel robots (CDPRs) are widely investigated and applied in the worldwide; however, traditional configurations make them to be limited in reaching their maximum workspace duo to constraints such as the maximum allowable tensions of cables. In this paper, we introduce auxiliary counterbalances to tackle this problem and focus on work...
This paper presents a novel adaptive multiple-model predictive control (MPC) scheme for Four-Wheel Independent Drive (4WID) autonomous vehicles with a holistic structure. Firstly, the combined vehicle-path model is established. To ensure the real-time performance of MPC, the coupling relationships in the control output and the longitudinal/lateral...
The concept of intelligent tires has drawn the attention of researchers in the areas of autonomous driving, advanced vehicle control, and artificial intelligence. The focus of this paper is on intelligent tires and the application of machine learning techniques to tire force estimation. We present an intelligent tire system with a tri-axial acceler...
This article focuses on the essential limitations of planar point-mass cable-driven parallel robots (CDPRs) in covering all poses of their footprint, which results in concave-shape static workspaces (SW) and also providing a zero force level on the borders of such a SW. Accordingly, a novel passive counterbalancing mechanism is proposed which not o...
Using a 3-degree-of-freedom lateral dynamic vehicle-trailer system model with the LuGre tyre model, this paper proposes a constrained unscented transformation based scheme for estimating the lateral velocity of a vehicle trailer. It is shown that the proposed lateral velocity estimation scheme is robust to the road condition. An affine quadratic st...
The uncertainties in tire cornering stiffness can degrade the path following the performance of autonomous vehicles, especially in low adhesive conditions, to deal with this problem, a novel multi-model adaptive predictive control is proposed in this study. Firstly, a model predictive path following controller is designed based on a combined model...
This paper presents redundancy resolution and disturbance rejection via torque optimization in Hybrid Cable-Driven Robots (HCDRs). To begin with, we initiate a redundant HCDR for nonlinear whole-body system modeling and model reduction. Based on the reduced dynamic model, two new methods are proposed to solve the redundancy resolution problem: join...
A closed-loop directed energy deposition (CDED) system is developed to control the microstructure and mechanical properties of laser additive manufactured material in real-time. An austenitic stainless-steel grade of S316-L, which avoids eutectoid phase transformation, is examined to evaluate this unique control technique's performance. A set of wa...
Considering a simplified model of cables is an essential assumption in the design of state-estimator and vibration control of cable-driven parallel robots (CDPRs). Such an assumption however, impacts the effectiveness of controllers and state-estimators in such systems. This article presents a reaction-based stabilizer for nonmodel-based vibration...
The concept of intelligent tires has drawn attention of researchers in the areas of autonomous driving, advanced vehicle control, and artificial intelligence. The focus of this paper is on intelligent tires and the application of machine learning techniques to tire force estimation. We present an intelligent tire system with a tri-axial acceleratio...
Understanding the dynamic behavior of tires and their interactions with road plays an important role in designing integrated vehicle control strategies. Accordingly, having access to reliable information about the tire-road interactions through tire embedded sensors is very demanding for developing enhanced vehicle control systems. Thus, the main o...
In this work, we propose a constrained moving horizon state estimation approach to estimate a pedestrian’s states in 3D with respect to a global stationary frame including position, velocity, and acceleration that are robust to intermittently noisy or absent sensor measurements. Utilizing a computationally light-weight fusion of a Deep Neural Netwo...
Trailer mass is one of the important trailer parameters that affects the stability of the tractor-trailer systems. In this paper, two different approaches are proposed to estimate trailer mass for arbitrary tractor-trailer configurations; dynamic system model-based and Machine Learning (ML) approaches. The stability of the dynamic system model-base...
Modular vehicles have great potential to solve future mobility challenges in an efficient, reliable and flexible way. Various designs have been proposed for compact and multi-functional wheel modules. However, the architecture of vehicular active safety systems, by adopting such a modular approach, has not yet been well studied in the literature. C...
This paper presents a control method based the lateral interconnected air suspension system, in order to improve the road handling of vehicles. A seven-DOF (Degree of freedom) full-vehicle model has been developed, which considers the features of the interconnected air suspension system, for example, the modeling of the interconnected pipelines and...
This article focuses on the static workspace (SW) of aerial cable towed robots (ACTRs) with land-fixed winches and provides an optimization approach to maximize the size of such a workspace. In the structure of the studied robots, land-fixed winches beside the ACTRs, actuated by unmanned aerial vehicles (UAVs), are used to manipulate a platform to...
Ethical decision-making during inevitable crashes, especially when humans involved, has become a big and sensitive roadblock for future mass adoption of autonomous vehicles. Towards addressing this challenge, this paper proposes a predictive control framework for ethical decision-making in autonomous driving using rational ethics. For flexibly impl...
This paper presents a model predictive vehicle stability controller that considers tire force nonlinearities and the combined-slip effect. Loss of cornering forces caused by increased longitudinal slip and changes in the slip angle due to the vehicle lateral response are considered in the prediction model of the controller. The developed controller...
Controlling the lateral dynamics of an autonomous vehicle confronting a sudden obstacle requires optimal use of tires' force capacities. In these situations, autonomous steering may not be able to respond fast enough to prevent collision or instability. This paper presents an integrated controller for autonomous vehicles, capable of suitably reacti...
This paper proposes an integrated stability control strategy for tilting vehicles. The work extends the envelope-based lateral stability controller by introducing and enforcing the roll envelope in the optimal control design. The model predictive controller (MPC) scheme is adopted to apply the control effort only when the predicted vehicle states a...
Different types of instability modes in tractor-trailer vehicles, including jackknifing and snaking, necessitate designing a fast and effective control strategy. In this paper, a model predictive controller (MPC) is developed to prevent these instability modes in a car-trailer vehicle as a specific form of tractor-trailer vehicles equipped with dif...