Rajesh Rajamani's research while affiliated with University of Minnesota Twin Cities and other places
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Publications (333)
This article focuses on estimating the position and orientation of a three degree-of-freedom (DoF) robot using a novel electromagnet-based active control system. The electromagnet is mounted on a servo motor and its orientation is controlled in real time so that it always points at the robot. A two-axis magnetic sensor on the robot helps determine...
This paper develops a position estimation system for a robot moving over a two-dimensional plane with three degrees of freedom. The position estimation system is based on an external rotating platform containing a permanent magnet and a monocular camera. The robot is equipped with a two-axes magnetic sensor. The rotation of the external platform is...
This paper develops a neuro-adaptive observer for state and nonlinear function estimation in systems with partially modeled process dynamics. The developed adaptive observer is shown to provide exponentially stable estimation errors in which both states and neural parameters converge to their true values. When the neural approximator has an approxi...
This paper presents the development of a novel prototype system to measure the profile of snow and detect ice on road surfaces. While researchers have previously developed methods to estimate the tire-road friction coefficient, methods to create a high resolution map of snow cover and ice on roads have not been developed. The prototype and data pro...
This paper focuses on activity recognition using a single wearable inertial measurement sensor placed on the subject's chest
.
The ten activities that need to be identified include lying down, standing, sitting, bending and walking, among others. The activity recognition approach is based on using and identifying a transfer function associated wit...
Inertial sensors have become increasingly popular in human activity classification due to their ease of use and affordability. This paper proposes a novel algorithm for human activity recognition that is a combination of a high-gain observer and deep learning computer vision classification algorithms. The nonlinear high-gain observer designed using...
The use of wearable sensors in movement disorder patients such as Parkinson’s disease (PD) and normal pressure hydrocephalus (NPH) is becoming more widespread, but most studies are limited to characterizing general aspects of mobility using smartphones. There is a need to accurately identify specific activities at home in order to properly evaluate...
This paper develops a multi-stage estimation algorithm for use on an e-scooter for target vehicle trajectory tracking. Previously designed observers for vehicle trajectory tracking lacked some essential features such as the ability to handle variable velocity, or stable performance in the presence of uncertainties in the measurements. To overcome t...
This paper develops a new approach to estimation of in-cylinder pressure and combustion variables for cycle-to-cycle combustion control in diesel engines. Such combustion control can lead to enhancement of engine performance and efficiency as well as prevention of combustion failures in UAV diesel engines. In-cylinder pressure and combustion variab...
This paper presents solutions to challenges in using a low-density flash lidar for application to a heavy road vehicle Autonomous Emergency Braking (AEB) system. Low-density flash lidars are relatively new to the commercial market and are much less expensive compared to point-cloud lidars. However, due to their low angular resolution, it becomes ch...
This article presents a wearable inertial measurement unit based system that estimates three-dimensional respiratory displacements on the thoracoabdominal surface. Such estimates can be useful in the calculation of respiratory rate, tidal volume, and for monitoring synchrony of compartments of the thoracoabdominal wall for diagnosis and physiothera...
This paper develops an electromagnet-based position estimation system for a cm-scale robot with two degrees of freedom. The orientation of an external electromagnet is actively controlled in realtime to maximize the magnetic field magnitude at the robot. This results in a monotonic relationship between the magnetic field magnitude and radial distan...
Accurate activity recognition has multiple useful health applications, including home-based monitoring in various chronic disease applications. This paper utilizes a deep-learning-based algorithm for recognition of various daily living activities. A nonlinear observer that estimates body segment tilt angles and sensor bias parameters, using inertia...
The use of wearable sensors in movement disorder patients such as Parkinson's disease (PD) and normal pressure hydrocephalus (NPH) is becoming more widespread, but most studies are limited to characterizing general aspects of mobility using smartphones. There is a need to accurately identify specific activities at home in order to properly evaluate...
Optical wireless communication is emerging as a low-power, low-cost, and high data rate alternative to acoustic and radio-frequency communications in several short to medium-range applications. However, it requires a close-to-line-of-sight link between the transmitter and the receiver. Indeed, a severe misalignment can lead to intolerable signal fa...
Light-Emitting Diode (LED) optical wireless communication is a potentially low-cost, sustainable approach for enabling high-speed free-space and underwater transmissions within a limited communication range. Establishing a tightly controlled line of sight (LOS) between transmitter and receiver is a significant challenge because the angle of the ali...
In this paper, a new electromagnetic angular position sensing method using high-magnetic-permeability metal (e.g., mu-metal) is proposed for measurement of joint angles of rotational mechanisms. An electromagnet and magnetic sensors are both located on one mechanical part and the mu-metal element is located on the other mechanical part with relativ...
In this letter, a new 3-D electromagnetic position sensing method is proposed for localization of continuum medical robots. An electromagnet and magnetic sensors are placed outside the human body while only a piece of passive mu-metal with high magnetic permeability is attached to the robot moving inside the body, resulting in a wireless non-contac...
This paper proposes a novel electromagnetic position estimation system suitable for piston-cylinder actuators using active current control. The inexpensive non-contacting position measurement system is composed of an electromagnet on the stationary cylinder and a magnetic sensor on the piston rod. The measured amplitude of an alternating magnetic f...
This work aims to estimate severe fMRI scanning artifacts in extracellular neural recordings made at ultrahigh magnetic field strengths in order to remove the artifact interferences and uncover the complete neural electrophysiology signal. We build on previous work that used PCA to denoise EEG recorded during fMRI, adapting it to cover the much lar...
This letter deals with observer design for a class of nonlinear systems. This letter makes two notable contributions. First, we propose a solution to design an observer for systems without global Lipschitz conditions by extending the nonlinearities to globally Lipschitz functions. Secondly, we provide a novel Linear Matrix Inequality (LMI) conditio...
This letter deals with observer design for a class of Lipschitz nonlinear systems. Specifically, we propose a mathematically rigorous technique to handle systems having non-globally Lipschitz properties on the whole set
$\pmb {\mathbb {R}}^{n}$
. The unique assumption made on the nonlinearity is for it to be Lipschitz on a compact convex set
$\O...
This paper develops a machine-learning-based method for counting vehicles and classifying their maneuvers in a traffic intersection using inexpensive low-density Lidar sensors. First, each vehicle is automatically detected using hierarchical clustering and then its trajectory is tracked using a virtual point method that compensates for the low angu...
This paper develops a novel algorithm for tracking closely-spaced road vehicles using a low-density flash lidar. Low-density flash lidars are recent to the automotive market and have attracted attention due to their low cost. However, these sensors have a poor angular resolution which makes tracking the lateral motion of targets challenging. One su...
This paper focuses on step length estimation using inertial measurement sensors. Accurate step length estimation has a number of useful health applications, including its use in characterizing the postural instability of Parkinson’s disease patients. Three different sensor configurations are studied using sensors on the shank and/or thigh of a huma...
This paper focuses on position estimation in smart actuators using non-contacting magnetic sensors. Magnetic position estimation in long-stroke actuators involves nonlinear non-monotonic measurement equations and the need to use more than one magnetic sensor. These challenges are addressed by developing a methodology for computing optimal sensor pl...
This paper focuses on step length estimation using inertial measurement units. Accurate step length estimation has a number of useful health applications, including its use in characterizing the postural instability of Parkinson’s disease patients. Three different sensor configurations are studied using sensors on the shank and/or thigh of a human...
This paper focuses on the removal of periodic artifacts from neural signals recorded in rats in ultra-high field (UHF) MRI scanners, using a reference free adaptive feedforward method. Recording extracellular neural signals in the UHF environment is motivated by the desire to combine neural recording and UHF functional magnetic resonance imaging (f...
Bicycling is a healthy physical activity for all ages. It can provide both physical and mental health benefits, including reducing the risk of cancer [1], cutting the risk of heart disease by half [2], postponing Alzheimer’s disease [3, 4], and promoting mental alertness and memory [5].
This paper addresses the problem of state estimation and simultaneous learning of the vehicles tire model on autonomous vehicles. The problem is motivated by the fact that lateral distance measurements are typically available on modern vehicles while tire models are difficult to identify and also vary with time. Tire forces are modeled in the estim...
Traditional electrodes used for neural recording and stimulation generate large regions of signal void (no functional MRI signal) when used in ultrahigh field (UHF) MRI scanners. This is a significant disadvantage when simultaneous neural recording/stimulation and fMRI signal acquisition is desired, for example in understanding the functional mecha...
This article focuses on state-of-charge (SoC) estimation for a lithium-ion battery modeled using a recently developed nonlinear double-capacitor representation that has been shown to be highly accurate. The measurement equation of the model has two nonlinear functions, one of them being significant hysteresis in voltage as a function of the SoC. Th...
This paper deals with new finite-time estimation algorithms for Linear Parameter Varying (LPV) discrete-time systems and their application to output feedback stabilization. Two exact finite-time estimation schemes are proposed. The first scheme provides a direct and explicit estimation algorithm based on the use of delayed outputs, while the second...
This article examines the problem of Lithium-Sulfur (Li-S) battery state estimation. Such estimation is important for the online management of this energy-dense chemistry. The literature uses equivalent circuit models (ECMs) for Li-S state estimation. This article’s main goal is to perform estimation using a physics-based model instead. This approa...
This study uses a low-density solid-state flash lidar for estimating the trajectories of road vehicles in vehicle collision avoidance applications. Low-density flash lidars are inexpensive compared to the commonly used radars and pointcloud lidars, and have attracted the attention of vehicle manufacturers recently. However, tracking road vehicles u...
This paper focuses on the dynamics of the COVID-19 pandemic and estimation of associated real-time variables characterizing disease spread. A nonlinear dynamic model is developed which enhances the traditional SEIR epidemic model to include additional variables of hospitalizations, ICU admissions, and deaths. A 6-month data set containing Minnesota...
This article examines the problem of Lithium-Sulfur (Li-S) battery state estimation. Such estimation is important for the online management of this energy-dense chemistry. The literature uses equivalent circuit models (ECMs) for Li-S state estimation. This article's main goal is to perform estimation using a physics-based model instead. This approa...
PURPOSE: Dupuytren disease (DD) has been associated with enlarged Pacinian corpuscles (PCs) and with PCs having a greater number of lamellae. Based on these associations, we hypothesized that subjects with DD would have altered sensitivity to high-frequency vibrations and that the changes would be more prominent at 250 Hz, where healthy subjects de...
Objective:
Removal of common mode noise and artifacts from extracellularly measured action potentials, herein referred to as spikes, recorded with multi-electrode arrays (MEAs) which included severe noise and artifacts generated by an ultrahigh field (UHF) 16.4 Tesla magnetic resonance imaging (MRI) scanner.
Approach:
An adaptive virtual referen...
This paper focuses on the development of a thin normal-shear force sensor based on the use of a supercapacitive sensing mechanism. The sensor has a quad structure with four sensing units in which the bottom substrate has four pairs of electrodes while the top deformable portion has a solid-state electrolyte. The application of normal and shear forc...
This paper focuses on the detection of cyber-attacks on a wireless communication channel and simultaneous radar sensor health monitoring for a connected vehicle. A semi-autonomous adaptive cruise control (SA-ACC) vehicle is considered which has wireless communication with its immediately preceding vehicle in the same lane. The wireless connectivity...
This paper focuses on the development of a system to detect if any car poses a collision danger to a bicycle, and to sound a loud horn to alert the car driver if a collision danger is detected. A sensing and estimation system suitable for use on a bicycle is therefore developed in order to track the trajectories of vehicles in a traffic intersectio...
This paper focuses on state‐of‐charge (SOC) estimation in a lithium‐ion battery, using measurements of terminal voltage and bulk force. A nonlinear observer designed using Lyapunov analysis relying on lower and upper bounds of the Jacobian of the nonlinear output function is utilized. Rigorous analysis shows that the proposed observer has feasible...
This paper develops a novel instrumented urethral catheter with an array of force sensors for measuring the distributed pressure in a human urethra. The catheter and integrated portions of the force sensors are fabricated by the use of 3D printing using a combination of both soft and hard polymer substrates. Other portions of the force sensors cons...
Estimating central aortic blood pressure is important for cardiovascular health and risk prediction purposes. Cardiovascular system is a multi-channel dynamical system that yields multiple blood pressures at various body sites in response to central aortic blood pressure. This paper concerns the development and analysis of an observer-based approac...
A pressure sensing catheter system includes a urethral catheter and a sensor array formed on the urethral catheter. The sensor array includes a plurality of pressure sensors distributed along a length of the urethral catheter. The sensor array is configured to produce a dynamic pressure distribution profile along a urethra.
This paper focuses on the challenges in observer design for nonlinear systems which are non-monotonic. A class of nonlinear systems is considered in which the process dynamics and output equations are both composed of nonlinear vector functions of scalar combinations of the states. The nonlinear functions are assumed to be differentiable with bound...
Alignment for maintaining Line-of-Sight (LoS) between the receiver and the transmitter in a LED optical communication system is a challenging problem due to the constant movement of the underlying optical platform that is caused by vibration effects and atmospheric turbulence. In this paper, we propose a robust switched-gain nonlinear observer to e...
The focus of this paper is on the development of a
vehicle-tracking algorithm using a solid-state LIDAR sensor for
application to Collision Avoidance Systems (CAS) for Heavy
Commercial Road Vehicles. Solid State LIDARs are relatively
inexpensive compared to RADARs and point cloud LIDARs,
and hence could accelerate commercialization of Advanced
Driv...
This paper develops an electromagnet-based position measurement system for industrial actuators which offers significant advantages compared to traditional position measurement systems. These advantages include low cost, non-contacting operation, easy installation and robustness to magnetic disturbances. In the first embodiment of the sensor, the e...
This paper addresses the problem of observer-based stabilization of discrete-time linear systems in presence of parameter uncertainties and ℓ2-bounded disturbances. We propose a new variant of the classical two-step LMI approach. In the first step, we use a slack variable technique to solve the optimization problem resulting from stabilization by a...
This article develops a fundamental new sensing principle for measuring the position of a moving object. The moving object is equipped with a thin film of high magnetic permeability. A stationary electromagnet and a magnetic sensor are located nearby. As the moving object’s position changes, the coupling between the electromagnet and the magnetic s...
This paper uses an inexpensive laser sensor mounted on a rotationally controlled platform to simultaneously search for and track vehicles that are behind a bicycle. Vehicles in the bicycle's lane and in the adjacent left lane are both considered. The tasks involved are searching both lanes to detect presence of vehicles, tracking a vehicle's trajec...
This paper develops a robust gain-scheduled proportional–integral–derivative (PID) controller design method for a linear-parameter-varying (LPV) system with parametric uncertainty. It is recognized in the literature that the robust fixed-order controller design can be formulated as a feasibility problem of a bilinear matrix inequality (BMI) constra...
This paper discusses a novel algorithm to automatically identify the position of a smartphone inside a moving vehicle, so as to detect whether it is being used by the driver or just a passenger of the car. This detection has applications to the prevention of distracted driving and can be used to automatically disable phone features such as texting...
Instrumented wearable device for measurement of physiological parameters
This paper deals with nonlinear observer design for a class of nonlinear systems with nonlinear output measurements. The proposed methodology is based on the use of Linear Matrix Inequalities (LMIs) to handle a problem of convergence criterion. Some new assumptions and convenient Young’s formulation are used to get less conservative LMI conditions...
This letter develops a novel strain sensor with ultra-high sensitivity and range that can be easily fabricated using a paper-based electrolyte and two metal pins bought from a local hardware store. No cleanroom facilities are needed. The sensor utilizes a fundamentally new sensing principle consisting of a paper-based solid-state electrolyte which...
This paper focuses on the development and use of a nonlinear observer for tracking of vehicle motion trajectories while using a radar or laser sensor. Previous results on vehicle tracking have typically used an interacting multiple model filter that needs different models for different modes of vehicle motion. This paper uses a single nonlinear veh...
This paper develops a new high-gain observer design method for nonlinear systems that has a lower gain compared to the standard high-gain observer. This new observer, called HG/LMI observer is obtained by combining the standard high gain methodology with the LMI-based observer design technique. Through analytical developments, the paper shows how t...
Abstract Paper has been pursued as an interesting substrate material for sensors in applications such as microfluidics, bio-sensing of analytes and printed microelectronics. It offers advantages of being inexpensive, lightweight, environmentally friendly and easy to use. However, currently available paper-based mechanical sensors suffer from inadeq...
Urinary incontinence can be due to neuromuscular or structural problems in either the bladder or the urethra. Urodynamics is often used to analyze the patient-specific cause of urinary incontinence. In urodynamics, a challenging part of the studies involves measurement of the urethral (contact) pressure profile. Here we present an instrumented uret...
The exact localization of signal recording probes or deep stimulation probes by magnetic resonance imaging (MRI) has significant importance in studying and understanding how the brain functions. But the magnetic susceptibility of the probes itself distorts the MRI image and creates error in position measurement. In this paper we propose an MRI comp...
Estimating attitude using an inexpensive MEMS inertial measurement unit has many applications in smart phones, wearable sensors, rehabilitation medicine and robots. Traditional approaches to attitude estimation from the aerospace world focus on the use of either Euler angles or quaternions. These approaches suffer from disadvantages including singu...
An observer for a nonlinear system may be required to satisfy multiple performance criteria such as minimum convergence rate and disturbance rejection, in addition to asymptotic stability. In such cases, the observer can no longer be designed using a linear matrix inequality. A bilinear matrix inequality (BMI) is needed instead and involves a non-s...
Fluid accumulation in the lower extremities is an early indicator of disease deterioration in cardiac failure, chronic venous insufficiency and lymphedema. At-home wearable monitoring and early detection of fluid accumulation can potentially lead to prompt medical intervention and avoidance of hospitalization. Current methods of fluid accumulation...
A two-step numerical computation of T2∗ signal weighting maps in gradient echo magnetic resonance imaging in the presence of an object with varied susceptibility property is presented. In the first step, the magnetic scalar potential is computed for an arbitrary 2D magnetic susceptibility distribution using an algebraic solver. The corresponding ma...
The proximity of a magnetic sensor to a magnet has been utilized for position measurement in many applications involving small ranges of motion. However, such position measurement becomes challenging when the application involves a ferromagnetic environment and larger ranges of motion. The movement of a magnet magnetizes and demagnetizes the ferrom...
Electrical stimulation of neural tissue is a promising therapy for a variety of neurological diseases. For example, electrical stimulation of deep thalamic nuclei has been used extensively to treat symptoms of Parkinson’s disease, and there is growing interest in treating other conditions including epilepsy and depression with similar techniques. H...
Urinary incontinence (UI), defined by the International Continence Society as “the complaint of any involuntary leakage of urine” [1], is believed to affect at least 13 million people in the United States. Around 80% of people affected are women [2,3]. The most common type of UI in women is stress urinary incontinence (SUI) [4]. Although not identi...
Citations
... Some publications use a high gain observer to provide data for machine learning. In [13] a classically designed high gain observer is used to improve the performance of a deep learning activity recognition algorithm. In [14], a high gain observer is used to estimate the position of a ship. ...
![[object Object]](https://i1.rgstatic.net/ii/profile.image/1023532230270982-1621040508585_Q64/Ali-Nouriani.jpg)
![[object Object]](https://i1.rgstatic.net/ii/profile.image/278694158454792-1443457273640_Q64/Robert-Mcgovern-4.jpg)
... The algorithm used to identify each home activity is a deep learning-based activity recognition architecture using a convolutional neural network with long short term memory cells (CNN-LSTM). The CNN-LSTM network implements a nonlinear observer for the estimation of the tilt angles of the human body limb segments as the input of the CNN layers followed by LSTM layers and finally fully connected layers with Softmax activation which we have detailed previously (Nouriani et al., 2022). We also used three other commonly used classifiers (logistic regression, support vector machine, decision tree) to compare their performance to our CNN-LSTM. ...
... This assumption is used in many papers such as [37,38]. ...
![[object Object]](https://i1.rgstatic.net/ii/profile.image/355523070316544-1461774713050_Q64/Ali-Zemouche.jpg)
... Estimation methods are often employed to observe the state of the system and create analytical redundancy for detecting attacks. Common techniques include Kalman filtering methods, such as the Kalman filter (KF) [23]- [25] and the unscented KF (UKF) [26], as well as observer-based methods [27]- [38] and sliding mode observation [39], [40]. ...