Tsu-Chin Tsao

University of California, Los Angeles | UCLA · Department of Mechanical and Aerospace Engineering

The performance of over-actuated Unmanned Aerial Vehicles (UAVs) is significantly influenced by aerodynamic effects, as they are subject to different airflow conditions. For those aerodynamic effects that are difficult to model but could occur repeatedly, Iterative Learning Control (ILC) has great potential to improve the system performance by lear...

Propeller failure is a major cause of multirotor Unmanned Aerial Vehicles (UAVs) crashes. While conventional multirotor systems struggle to address this issue due to un- deractuation, over-actuated platforms can continue flying with appropriate fault-tolerant control (FTC). This paper presents a robust FTC controller for an over-actuated UAV platfo...

Propeller failure is one major reason for the falling and crashing of multirotor Unmanned Aerial Vehicles (UAVs). While conventional multirotors can barely handle this issue due to underactuation, over-actuated platforms can still pursue the flight with proper fault-tolerant control (FTC). This paper investigates such a controller for one such over...

This paper presents the control and experiments of a novel multirotor aerial platform, which is capable of full actuation for six Degree of Freedom (DoF) motions. The platform is actuated by a number of tilting-thrust modules, each consisting of a regular quadcopter and a mechanically passive hinge. The platform in this paper has four such actuator...

Within cataract surgery, posterior capsule (PC) polishing is a specific procedure that has demonstrated value toward improving surgical outcomes, yet is not commonly performed by surgeons due to the risk of doing so. In this work, a robotic system is used to perform the polishing procedure through three main contributions: external stabilization of...

Iterative learning control (ILC) has proven successful in the industry for enhancing tracking performance of repetitive tasks. The high accuracy and fast convergence of ILC algorithms hinge on: 1) the knowledge of the system model and 2) an effective learning algorithm. For general industrial systems with nonlinear dynamics, this raises technical c...

This paper presents the control and experiment of a novel multirotor aerial platform, which is capable of full actuation for six Degree of Freedom (DoF) motions. The platform is actuated by a number of tilting-thrust modules, each consisting of a regular quadcopter and a mechanically passive hinge. The platform in this paper has four such actuator...

Overactuated multirotor unmanned aerial vehicles (UAVs) usually consist of multiple tiltable thrust actuators. The controllers are mostly designed by regarding the thrust forces and actuator tilting angles as inputs of outer-loop position and attitude controllers, while formulating an inner-loop controller for each actuator to track the thrust and...

Discrepancies between the needle feature position on magnetic resonance imaging (MRI) and the underlying physical needle position could increase localization errors during needle-based targeting procedures in MRI-guided percutaneous interventions. This work aimed to develop a deep learning-based framework to automatically localize the physical need...

Multirotor copters with full six Degree of Free-dom(DoF) maneuvering are often overactuated. The control allocation of overactuated UAV platforms can have an infinite number of solutions due to their redundancy. The most common allocation framework is based on Force Decomposition(FD), which provides a robust least-square solution and is easy to imp...

Conventional multirotors have coupling between position and attitude control due to underactuation in dynamics, and thus can not track six degree-of-freedom (DoF) trajectories in space. Previous works proposed fully actuated multirotors with modifications to mechanical structure to provide varying orientations of thrust forces without changing the...

Multirotor copters with full six Degree of Freedom (DoF) maneuvering are often overactuated. The control allocation of overactuated UAV platforms can have an infinite number of solutions due to their redundancy. The most common allocation framework is based on Force Decomposition (FD), which provides a robust least-square solution and is easy to im...

The overarching goal of this letter is to demonstrate the feasibility of using optical coherence tomography (OCT) to guide a robotic system to extract lens fragments from ex vivo pig eyes. A convolutional neural network (CNN) was developed to semantically segment four intraocular structures (lens material, capsule, cornea, and iris) from OCT imag...

Common error sources of industrial robot manipulators include joint servoing error, imprecise kinematics, mechanical compliance, and transmission error. In this work we present a nested loop iterative learning control (ILC) feedforward structure: an inner loop that compensates for motor dynamics, and an outer loop that corrects the deviation along...

Background: In cataract surgery, polishing of the posterior capsule (PC) can lead to improved surgical outcomes but is currently avoided due to its high-risk nature. This work developed a robotic system capable of performing PC polishing on ex vivo pig eyes using optical coherence tomography (OCT) guidance. Methods: The lenses of five ex vivo pi...

This work aims to quickly identify an FIR inverse dynamical model for linear time-invariant (LTI) systems. Various applications are enabled using the constructed inverse filter, as illustrated by an inversion-based iterative learning control (ILC) algorithm. With the help of interleaving inversion-based ILC and ILC-based inverse dynamics identifica...

Retinal vein occlusion is one of the most common causes of vision loss, occurring when a blood clot or other obstruction occludes a retinal vein. A potential remedy for retinal vein occlusion is retinal vein cannulation, a surgical procedure that involves infusing the occluded vein with a fibrinolytic drug to restore blood flow through the vascular...

PurposeAccurate needle tracking provides essential information for MRI-guided percutaneous interventions. Passive needle tracking using MR images is challenged by variations of the needle-induced signal void feature in different situations. This work aimed to develop an automatic needle tracking algorithm for MRI-guided interventions based on the M...

Background Stack‐of‐radial multiecho gradient‐echo MRI is promising for free‐breathing liver quantification and may benefit children. Purpose To validate stack‐of‐radial MRI with self‐gating motion compensation in phantoms, and to evaluate it in children. Study Type Prospective. Phantoms Four vials with different driven by a motion stage. Subje...

One of the main challenges in MRI-guided interventions is for an instrument to access and track a respiration-induced moving target inside the patient. We present a mechatronic system that demonstrates such capability for one-dimensional motion in phantom experiments. Our system consists of real-time sensing by MRI acquisition, detection, and local...

This article presents a novel design and experiment of a system of hydrostatic actuation, transmission network, and control as a research platform for investigating magnetic resonance image (MRI) based tracking and intervention of a moving target. Based on novel double-acting piston-cylinder type rolling diaphragm fluid actuators, the system compri...

A novel method to construct dynamic inversion compensation is proposed for feedforward tracking control. In contrast to common approaches involving parametric system identification followed by inversion synthesis, in this paper we apply Iterative Learning Control (ILC) to track an impulse signal, where the converged control input is directly used t...

This paper presents a novel adaptive feedforward control (AFC) method for rejecting sinusoidal disturbances with known frequencies acting on multi-input-multi-output (MIMO) discrete time linear systems based on the H-infinity synthesis. First, the gradient AFC (GAFC) for MIMO systems is reviewed, and the linear time invariant (LTI) equivalent form...

Background: Magnetic resonance imaging (MRI) has unique advantages for guiding interventions, but the narrow space is a major challenge. This work evaluates the feasibility of a remote-controlled hydrostatic actuator system for MRI-guided targeted needle placement. Methods: The effects of the hydrostatic actuator system on MR image quality were...

Purpose: To evaluate semiautomated surgical lens extraction procedures using the optical coherence tomography (OCT)-integrated Intraocular Robotic Interventional Surgical System. Setting: Stein Eye Institute and Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, USA. Design: Experimental study. Methods:...

The aim of this work is to propose a data-driven ILC algorithm that features fast convergence for nonlinear dynamic systems. This idea utilizes adaptive filtering that implicitly identifies the time-varying system inverse along the trajectory being tracked. By feeding the error signal through the copied inverse filter, it results in a rapidly conve...

A laparoscopic surgical training system, the LapaRobot, is introduced. The system is composed of an expert station and a trainee station connected through the Internet. Embedded actuators allow the trainee station to be driven by an expert surgeon so that a trainee learns proper technique through physical feedback. The surgical‐tool trajectory and...

Objective: Magnetic resonance imaging (MRI) can provide guidance for interventions in organs affected by respiration (e.g. liver). This study aims to: 1) investigate image-based and surrogate-based motion tracking methods using real-time golden-angle radial MRI; and 2) propose and evaluate a new fusion-based respiratory motion prediction framework...

Purpose: We determine whether haptic feedback improves surgical performance and outcome during simulated a preretinal membrane peeling procedure. Methods: A haptic-enabled virtual reality preretinal membrane peeling simulator was developed using a surgical cockpit with two multifinger haptic devices. Six subjects (three trained retina surgeons a...

To improve the tracking performance of industrial robot manipulators, a nested-loop iterative learning control (ILC) structure is presented. It consists of an inner loop that deals with drive dynamics, and an outer loop which addresses impreciseness of kinematic parameters as well as joint static bias. A data-based frequency inversion technique wit...

A mechanism consisting of twisting and tilting joints is introduced to provide omnidirectional thrust-vectoring capabilities to a quadrotor system. This mechanism eliminates mechanical constraints and kinematic singularities to provide full directional authority to all four individual thrust vectors. The presented system fully decouples position an...

Background: With the development of laser-assisted platforms, the outcomes of cataract surgery have been improved by automating several procedures. The cataract-extraction step continues to be manually performed, but due to deficiencies in sensing capabilities, surgical complications such as posterior capsule rupture and incomplete cataract remova...

An online fast path following control algorithm subject to contouring error tolerance and other prototypical constraints, analogous to a racing car within track boundaries, is presented. A receding horizon quadratic programming (QP) for real-time implementation on electromechanical systems is proposed. A key feature of the algorithm is that the cha...

This paper addresses precision tracking control of dual-stage actuators for machining of non-circular engine piston profiles. To achieve desired tracking performance, the capacity limits, dynamic characteristics, external disturbances, and model uncertainties of the dual-stage actuators pose significant challenges in the control design and real-tim...

Background: Since the advent of robotic-assisted surgery, the value of using robotic systems to assist in surgical procedures has been repeatedly demonstrated. However, existing technologies are unable to perform complete, multi-step procedures from start to finish. Many intraocular surgical steps continue to be manually performed. Methods: An i...

This paper proposes and studies the use of industrial robot manipulators to act as an active steady rest in machining thin-walled workpieces to prevent machining chatter instability. Feedback control is applied to the robotic steady rest in contrast to the other more popular active control method where the cutting tool is controlled. The entire dyn...

This paper addresses the error convergence rate of data-driven iterative learning control (ILC) for single-input-single-output (SISO) systems. Since the error convergence rate depends on the learning filter, which ideally should invert the plant dynamics, the challenge lies in creating the ILC learning filters that approximate the plant inverse wit...

We present the development of a system that physically emulates respiratory motion for phantoms under Magnetic Resonance Imaging (MRI). The system is designed to be inherently MR-compatible—with no ferrous materials or electromagnetic actuators present in the exam room—and uses hydrostatic actuators to control motion of the phantom. MR-compatibilit...

We present the identification and control of an open loop unstable MIMO Active Magnetic Bearing Spindle (AMBS) for machining applications. A 20th order model is obtained from reducing a higher order model identified by the ARX method. For verification purposes, the model is compared to the system’s frequency responses obtained by the frequency swee...

Different from previous work discussing how to improve the performance of the ILC algorithm by assigning a well-approximated plant inversion as the learning filter, a novel way to reconstruct a feedforward filter from the ILC algorithm is presented. Assuming the ILC algorithm has already been implemented for the controlled plant, a stable FIR feedf...

Maskless nanolithography is an agile and cost effective approach if their throughputs can be scaled for mass production purposes. Using plasmonic nanolithography (PNL) approach, direct pattern writing was successfully demonstrated with around 20 nm half-pitch at high speed. Here, we report our recent efforts of implementing a high-throughput PNL pr...

This paper builds upon previous work on modeling and controlling an organic Rankine Cycles (ORC) used for heavy-duty diesel powertrain. The novel contribution of this paper is operating the ORC as a base load regulating waste heat recovery (WHR) system in addition to the pressure regulation examined in previous work. Specifically, the expander powe...

Rotor unbalance, common phenomenon of rotational systems, manifests itself as a periodic disturbance synchronized with the rotor's angular velocity. In active magnetic bearing (AMB) systems, feedback control is required to stabilize the open-loop unstable electromagnetic levitation. Further, feedback action can be added to suppress the repeatable r...

This paper develops an automated vascular access system (A-VAS) with novel vision-based vein and needle detection methods and real-time pressure feedback for murine drug delivery. Mouse tail vein injection is a routine but critical step for preclinical imaging applications. Due to the small vein diameter and external disturbances such as tail hair,...

The learning filter in Iterative Learning Control determines the performance in terms of convergence rate and converged error. The ideal learning filter is the inverse of the system being learned. For minimum phase system, direct system inversion can be implemented easily. However for non-minimum phase system, direct system inversion would result i...

The present disclosure is directed to improved phacoemulsification procedures involving the use of processed non-visual three-dimensional data (i.e. diagnostic scan data) to provide a surgeon with additional guidance concerning the distance separating a working end of a phacoemulsification instrument and the posterior capsule of the eye during a su...

This paper uses a new method for receding-horizon adaptive control to reduce laser beam jitter. The control scheme generates a control command derived from a receding-horizon performance index that involves predicted future values of an output disturbance. A recursive least-squares adaptive lattice filter performs the required prediction based on r...

Precision motion control is often challenged by asynchronous sensor update and quantization noise, causing abrupt and untimely state variation to limit the machine precision. To provide smooth and accurate sensor interpretation, this study developed a novel event-triggered sub-count estimation method that addresses continuity on system states. By e...

This paper continues the development of a previous conference paper that introduces advanced controllers for an Organic Rankine Cycle (ORC) in a heavy-duty diesel powertrain. The ORC's heat exchangers are modeled as control-oriented, nonlinear Moving Boundary models. The pump and expander, which are coupled to the engine crankshaft, have relatively...

Discrete-time domain Iterative Learning Control (ILC) schemes inspired by Repetitive control algorithms are proposed and analyzed. The well known relation between a discrete-time plant (filter) and its Markov Toeplitz matrix representation has been exploited in previous ILC literature. However, this connection breaks down when the filters have nonc...

This paper presents controller designs for a nonlinear Organic Rankine Cycle (ORC) model used for transient waste heat recovery (WHR) in heavy-duty diesel powertrain. The ORC's heat exchangers are described by Moving Boundary models based on energy and mass conservation principles. The control-oriented, dynamic heat exchanger models are connected t...

A common problem in the operation of rotors is the sinusoidal disturbance caused by mass unbalance. Mass unbalance manifests as a harmonic force with frequency synchronous to the rotor speed. In a rotor-bearing system using Active Magnetic Bearings (AMBs), this issue is especially important as the gap between the rotor and electromagnets is small a...

This paper addresses the contour tracking time duration minimization problem subject to physical constraints of system dynamics, contour error, axial velocity, signal saturation, and monotonic feed. This finite horizon minimum time optimal control problem is approximated and formulated as a receding horizon optimal control, i.e. generalized predict...

This paper presents a stable inversion of nonminimum phase systems with highly efficient computation for high-sampling rate applications. The stable filter that inverts the dynamics of a nonminimum system is based on cascading a stable pole-zero cancellation infinite impulse response (IIR) filter with a high-order finite impulse response (FIR) filt...

This paper proposes an adaptive control scheme that minimizes the least-mean-square (LMS) value of the plant output while meeting the constraints of canceling deterministic exogenous signals generated by a priori dynamics. This scheme may be applied to a broad range of applications in which the exogenous input signals to the plant contain both dete...

This paper develops an efficient vision-based real-time vein detection algorithm for preclinical vascular insertions. Mouse tail vein injections perform a routine but critical step in most preclinical applications. Compensating for poor manual injection stability and high skill requirements, Vascular Access System (VAS) has been developed so a trai...

This paper presents results for nonlinear state estimation of a nonlinear, control-oriented Moving Boundary heat exchanger model derived from energy and mass conservation principles. The estimator design assumes pressure and temperature measurements typically available in waste heat recovery (WHR) applications. An Extended Kalman Filter (EKF) and a...

A control oriented formulation of continuous structures interacting with moving and/or fixed structures is presented. Machining of long parts in a lathe is presented in order to illustrate the methodology. The system is time-varying in nature due to the movement of the cutting tool during the machining process. However the invariant part correspond...

Murine models are used extensively in biological and translational research. For many of these studies it is necessary to access the vasculature for the injection of biologically active agents. Among the possible methods for accessing the mouse vasculature, tail vein injections are a routine but critical step for many experimental protocols. To per...

The paper presents a fixed-point realization of non-minimum phase system inversion for inversion based control algorithms such as feedforward, repetitive controller, and iterative learning control. Based on the author's previous work on efficient dynamic inversion using stable pole-zero cancelation and non-minimum phase zero inversion using Kurosu...

PurposeThe aim of this study is to develop a novel robotic surgical platform, the IRISS (Intraocular Robotic Interventional and Surgical System), capable of performing both anterior and posterior segment intraocular surgery, and assess its performance in terms of range of motion, speed of motion, accuracy, and overall capacities.Patients and method...

This paper presents a model predictive control based optimal feedforward tracking integrated with a robust repetitive feedback control aimed for generating complex engine piston profiles in non-circular engine piston turning using dual-stage long stroke linear motor/high bandwidth piezoelectric actuators. By formulating and solving receding horizon...

In this article we describe the design of a universal ultra-precision positioning platform to be used in the development of many different nano-manufacturing processes. The system incorporates the concept of employing different interchangeable manufacturing and characterization tools with one ultra-precision positioning system. A multi-linear-motor...

This paper presents the design and implementation of an integrated two-period repetitive and adaptive control scheme to reject both repeatable and nonrepeatable disturbances in the track-following servo control of a hard disk drive read-write head. A baseline linear quadratic Gaussian controller is augmented by a plug-in repetitive controller to re...

In this paper minimum power commutation laws of permanent-magnet synchronous linear motors are extended to multiple-motor driven systems. A system-wide view of commutation is shown to exploit the redundancy of motor coils and motor force generation that exist in over actuated motion platforms. We propose a novel commutation law, that is only realiz...

This paper investigates target tracking control for a high intensity focused ultrasound (HIFU) transducer to follow liver motion induced by respiratory cycles. Motivated by the apparent respiratory cycles repetitive control is first considered. Adaptive control, which employs recursive least squares adaptive filtering to minimize the tracking error...

This paper presents an investigation of the control problem of aiming a laser beam under dynamic disturbances, using light intensity for feedback only. The idea is to steer the beam with a biaxial microelectromechanical mirror, which is driven by a control signal generated by processing the beam intensity sensed by a single photodiode. Since the po...

This paper presents a robustness-enhanced adaptive control scheme and application to an experiment for the focusing of an optical read-write head for optical data storage drives. Minimum-variance adaptive controllers have applied recursive least-squares algorithms to predict output disturbance and dynamically compute control commands to minimize th...

In incorporating an internal model (IM) to an linear time invariant (LTI) feedback system to achieve asymptotic regulation for exogenous disturbances, limitation in robust stability often hinders the transient response performance, such as the convergence rate and maximum output magnitude, of the LTI closed loop system. When the onset time of the d...

This paper presents an adaptive control scheme and experimental results for the focusing of an optical read-write head for optical data storage drives. The adaptive control applies recursive least squares (RLS) algorithm to predict output disturbance and dynamically computes control commands to minimize the output focusing error. The adaptive contr...

This paper considers the Laguerre based adaptive control of piezoelectric actuator for nanopositioning. Laguerre-based adaptive filters provide an attractive alternative to adaptive FIR filters in the sense that they provide better approximation of system with a long impulse response with a restricted order. Laguerre also keeps many of the advantag...

Robotic intraocular microsurgery requires a remote center of motion (RCM) at the site of ocular penetration. We designed and tested the Hexapod Surgical System (HSS), a microrobot mounted on the da Vinci macrorobot for intraocular microsurgery. Translations and rotations of the HSS were tested for range of motion and stability. Precision and dexter...

This paper considers a fixed-point realization of approximate stable inversion of systems with non-minimum phase zeros. It is based on the efficient linear phase IIR filter implementation first introduced by Powell and Chau. The proposed filter is used in inversion based feedforward tracking and repetitive controllers which is realized by a Field P...

This paper presents the pedagogy of digital control design and experiment for a magnetic bearing system as part of a graduate level digital control class. The system identification verifies the system model structure, where the unstable MIMO system is kinematically de-coupled into SISO systems with model uncertainty bounds characterized for robustn...

This paper addresses commutation laws of brushless motor coils for multiple-degree-of-freedom motion. By exploiting the redundancy of motor coils and motor force generation that exist in over actuated motion platforms, we propose a commutation law, which generates the required forces while minimizing the effect of motor coil heat generation on ther...

A field test experiment on a range tracking telescope at the U. S. Army's White Sands Missile Range is exploring the use of recently developed adaptive control methods to minimize track loop jitter. Gimbal and platform vibration are the main sources of jitter in the experiments, although atmospheric turbulence also is a factor. In initial experimen...

This paper introduces a new method for synthesizing multiple-period repetitive controllers. The main innovations in the synthesis procedure presented in this article are two. The first one is that this technique yields a solution compatible with the integration of the computed multiple-period repetitive controller into a minimum-variance adaptive c...

This paper presents the design of an adaptive- Q control algorithm for minimizing the position error signal (PES) in a hard-disk-drive track-following servo. Also, we discuss the results obtained from experiments done on a commercial disk drive using the said scheme. The adaptive- Q control algorithm approach uses the well-known result that all sta...

This paper addresses the measurement of the location and precision of stationary points in the three dimensional space, commonly termed remote center of motion (RCM), of minimally invasive surgical robotic manipulators. Two-view computer vision is used for its versatility, portability, remote sensing, and cost effectiveness. Geometrical models of c...

A prototype tool stage with a variable rake angle mechanism has been developed and controlled. The objective of the variable rake angle mechanism is to provide two-degrees-of-freedom to the conventional noncircular turning process, so that the rotational tool mechanism can compensate for the rake angle change caused by the noncircular cam profile i...

This paper presents an investigation of the design and implementation of minimum-variance adaptive controllers for computer hard disk drive (HDD) read-write track following. A common characteristic of minimum-variance controllers, adaptive or not, is that they rely on prediction filters with large high- frequency gains to predict broadband disturba...

This paper introduces a new method for synthesizing multiple-period repetitive controllers, which are suitable for integration into a combined adaptive-repetitive control scheme. The proposed synthesis method can be implemented recursively reducing the complexity of controller design considerably when compared with other methods available in the li...

Based on a reduced order state-space model of an MBC 500 magnetic bearing system with fixed shaft (i.e. non rotating), two different observer-based digital controllers are designed to regulate the shaft. One is a robust linear pole-placement controller, and the other is a sliding mode controller. Each controller’s performance is mathematically anal...

Internal combustion engines can be modified to operate regenerative braking cycles by using compressed air power. This paper presents a particular air hybridization design from among many possible configurations. The engine cycles are enabled by a highly flexible engine valvetrain, which actuates engine valves to generate desired torque with optima...

This paper presents an investigation of the control problem of aiming a laser beam under dynamic disturbances, using light intensity for feedback. The beam is steered with a bi-axial MEMS mirror, which is driven by a control signal generated by processing the beam intensity sensed by a single photodiode. Since the pointing location of the beam is a...

This paper presents a method to synthesize internal model principle type controllers for rejection of sinusoidal disturbances. The frequencies of the disturbance are not required to be of rational ratios of the sampling interval or each other, thus addressing both periodic and aperiodic signals. The control synthesis utilizes positive feedback arou...