48 accepted papers
Among the many choices in the matrix-vector factorization of the Coriolis and centripetal terms satisfying the skew-symmetry condition in system dynamics, the unique factorization, called Christoffel-consistent (CC) factorization, has been proposed. We derived the unique CC factorization in the Lie
Impedance control is a widely adopted approach that ensures the compliant behavior of robot manipulators as they interact with their environment according to specifically designed dynamics. For tasks involving six degrees of freedom (DoF), it is crucial to appropriately manage the position and orien…
Additive manufacturing offers extensive design freedom but remains limited by path planning strategies that rely on planar slicing, which introduce staircase artifacts. Non-planar slicing improves local fidelity yet still produces stacking artifacts due to exposed layer boundaries, leaving a gap in …
Direct teaching in collaborative manipulators, an essential method for intuitive trajectory control, faces significant challenges due to friction in robot joints. To address this, we present a novel friction compensation framework to improve direct teaching methods for robots. Our approach focuses o
This work proposes a path generation policy for self-actuating soft grippers by converting external deformation conditions into intrinsic load conditions. This transformation enables anisotropic material orientation control of functional materials — which can deform under stimuli — aligning with the
This paper proposes an optimization-based control framework for the torque-controlled robot, which can satisfy the joint position, velocity, and acceleration constraints under a bounded jerk. The optimization filter is incorporated as a module to modify the nominal controller output to ensure joint…
In unilateral teleoperation systems, robots often face challenges when performing tasks with specific geometric constraints. These constraints restrict the robot's movements to certain directions, requiring accurate control of its position and orientation. If the operator's commands do not consider
Vacuum grippers are popular for their simplicity, reliability, and strength. However, their rigidity limits them to grip only relatively flat objects. To design a soft vacuum gripper, leakage through a suction cup must be prevented if the suction cup is not in contact with the object. Various soft v
This paper proposes a control structure for accurate tracking and compliant behavior of industrial manipulators without additional sensors. To achieve control objectives, friction, one of the biggest causes of performance degradation, should be compensated. For tracking performance, the estimated fr…
This paper proposes a teleoperation framework to exploit the maximum manipulation capability during teleoperation. Here, exploiting maximum manipulation capacity means that the robot moves with its maximum control input while not violating the given constraints, and it is a nonlinear optimization pr…
This paper analyzes the effect of control param-eters of feed-forward and inner loop velocity controller in an admittance control scheme on the performance and passivity. The interaction force, inertia, and damping compensation were considered as the feed-forward input. Sufficient conditions and gui…
Non-linear dynamics, model uncertainties due to hydraulic fluid, and disturbances in hydraulic systems make it difficult to obtain accurate torque tracking performance. In this study, a learning-based torque-tracking method is proposed, which does not require approximating the torque dynamics. The p…
This paper proposes an admittance controller-based teleoperation system for contact-rich tasks. Based on the analysis of the motivating task (deposited iron lump removal task in the steel mill), the system concept is focused on the practical aspects of the system, and various components are combined…
This article proposes deep learning based real-time optical coherence tomography (OCT) image segmentation and correction algorithm for vision-based robotic needle insertion systems that can be used in DALK (deep anterior lamellar keratoplasty) surgery. The proposed algorithm provides the position of
This letter proposes a novel backdrivable servovalve to implement a torque-controlled electro-hydraulic actuator. The proposed backdrivable servovalve simultaneously contains the characteristics of a flow-control servo valve (=feedback spring) and a pressure-control servovalve (=pressure feedback po
Surface electromyography contains muscular information representing gestures and corresponding forces. However, conventional sEMG-based motion recognition methods, such as pattern classification and regression, have intrinsic limitations due to the complex characteristics of sEMG signals. In this pa…
This paper presents a robust compliance control scheme for an electro-hydraulic robot manipulator with an electrohydraulic torque actuators (EHTAs) and joint torque sensors. The EHTA, a torque-sourced hydraulic actuator, consists of electrohydraulic backdrivable servovalve and a rotary hydraulic van
Robust particle manipulation is a challenging but essential technique for single-cell analysis and processing of microfluidic devices. This paper proposes a micro-particle manipulation system with a microfluidic channel network. We built gravity-induced pressure actuators, which can generate high-re…
The interpretation of surface electromyographic (sEMG) signals facilitates intuitive gesture recognition. However, sEMG signals are highly dependent on measurement conditions. The relationship between sEMG signals and gestures identified from a specific subject cannot be applied to other subjects ow
In this study, a forward dynamics-based control (FDC) framework is proposed for task space control of a nonredundant robot manipulator. The FDC framework utilizes forward dynamic robot simulation and an impedance controller to solve the inverse kinematics problem. For the practical use of the propos
With increased human-robot interactions in industrial settings, a safe and reliable collision detection framework has become an indispensable element of collaborative robots. The conventional framework detects collisions by estimating collision monitoring signals with a particular type of observer,
This letter proposes an intrinsically backdrivable electro-hydraulic torque actuator (EHTA) and associated control algorithms that could lead to the design of a high-performance interactive robot system. The EHTA consists of (electro-hydraulic) backdrivable servovalves and double vane rotary hydraul
Surface electromyograms (sEMG), are records of electrical signals generated by muscles, and have long been used to indicate the motions intended by humans to enable interactions between a robot and a human. To support not only the diverse movements in human daily living but also the task of increasi
Muscle activation signals are measured from the skin surface as surface electromyography (EMG) signals that contain information on human intentions; therefore, they are widely used in various robotics applications owing to their usability. However, selective muscle activation extraction is difficult…
Skin impedance should be minimized to obtain reliable and precise surface electromyography (sEMG) signals. High skin impedance decreases sensitivity to muscular activation and makes sEMG signals vulnerable to external noise. Microneedle-based electrodes have been proposed to achieve low skin impedan…
Sensory information from an Earth-fixed reference is necessary to guarantee a high localization accuracy of an unmanned underwater vehicle (UUV). However, the implementation of these sensors in an underwater environment is challenging because of signal uncertainties and strong signal attenuation. In…
The human finger exhibits fine motor skills that are widely used in daily activities. Thus, the motion estimation of a moving finger has several potential applications. Several surface electromyography interfaces have been proposed to estimate finger motion by analyzing finger-related muscles. Howev
Most commercial optical sorting systems are designed to achieve high throughput, so they use a naive low-latency image processing for object identification. These naive low-latency algorithms have difficulty in accurately identifying objects with various shapes, textures, sizes, and colors, so the p
Many robotics applications involving contact with objects require the decomposition of an external force measured by a force sensor into its normal and shear components. In this paper, we present a general and effective contact force decomposition method based on the contact pressure distribution. T
Position-based proportional derivative (PD) controllers are known to be able to render compliant behaviors to a robot, and they are usually used in conjunction with a friction compensator to improve control performance. Existing methods are effective when applied to actuation systems with mechanical…
There has been consistent trials to make a hydraulic actuator to be effective in interactive robot applications that require high power and durability. However, conventional strategies to obtain this goal, such as force/torque servo control or adding elastic components, suffer from complexity, senso…
A position-based proportional-derivative (PD) controller with inner torque feedback loops can be used as a simple controller to render compliant behaviors to hydraulic robots. However, using this control framework involves a tradeoff between the stability and performance of the closed-loop system (w…
Previously, we proposed a scheme that determines the position of a remotely operated underwater vehicle (ROV) from the signal strengths of commercial radio-frequency sensors and antennas. This scheme provides accurate position information in a structured environment but is limited to two-dimensional
Admittance control is a well-established and popular control strategy in modern robotics. However, the standard admittance controller has several limitations. First, the passivity can be guaranteed by finding a set of control parameters that makes the admittance function positive real. However, this…
Inertial microfluidics has facilitated promising applications of lab-on-a-chip devices for high-throughput biological analysis. However, as the mechanism of inertial microfluidics remains largely unknown, there are many difficulties in obtaining the desired equilibrium positions; hence, most researc
This paper proposes joint torque servo control of an electro-hydrostatic actuator (EHA) for effective dynamic control of robot manipulators. In the control design, the fluid parameters are not considered to develop a simple low-level controller used for multi degree-of-freedom (DOF) robot manipulato…
Microneedle insertion is useful for elucidating the processes in living cells and their organelles. However, mechanical puncture by the needle causes traumatic damage to the cell. As a less invasive process, we have developed intracellular needle insertion using femtosecond laser cell ablation. To q…
The human hand shows complex motor skills and is widely used in activities in daily living. Thus, finger movement recognition has many potential applications in rehabilitation, tele-operation, and prosthetic hands. Several surface electromyography (sEMG) interfaces have been developed to recognize f
This paper proposes a simple model-free joint torque control strategy for hydraulic robots. The undesirable effect called “natural velocity feedback effect” is discussed by introducing mechanical impedance of the system. The proposed model-free joint torque control consists of internal-loop control
We propose a fluidic monostable multivibrator (fMMV) circuit, which is a new flow-switching mechanism in microfluidic chips. Flow control using parallel fMMV circuits does not require an external controller; this is a distinct advantage over various conventional micro-flow control methods. The fMMV…
This paper proposes a passivity-based nonlinear disturbance observer (DOB) design for a powered upper-limb robot control. The proposed DOB allows for the nonlinearities of the robot dynamics, whereas the typical DOB designs cannot. Moreover, by virtue of the passivity property, human operator and en
We developed a ‘hybrid actuator system’ to precisely control the position of a micro-particle at high speed in a microfluidic chip. The hybrid actuator system benefits from two actuator systems by combining an electroosmotic flow generator and pressure-driven flow induced by a piezoelectric actuator…
Carrying unknown heavy payload is one of the classical problems in robotics. To realize heavy payload capability, the use of high reduction gears, which causes large motor-side inertia and large friction, is inevitable. This paper proposes a disturbance observer (DOB)-based approach that (1) reduces…
Dynamic motion of human shows kinematic aspects related to storing elastic energy in skeletal muscle. This results from joint stiffness modulation and as a consequence, countermovement which is opposite to the intended motion is observed. We propose a segmentation algorithm based on a hidden semi-Ma…
This paper presents a novel indicator for lump detection that uses only contact pressure distribution, as well as its feasibility evaluation. The conventional lump detection methods are based on a pressure map obtained from contact pressure distributions, but they requires an adequate regulation of…
We propose a novel flow control method to realize flow regulation and valveless flow switching in a microfluidic network. The proposed controller enables precise regulation of flow rates (or velocity fields) in micro-channels regardless of model uncertainties such as cross-sectional area and microch…
A series elastic actuator (SEA) consists of a system with an intrinsically compliant mechanism, and introduces the possibility of external force/torque sensing and control. However, this mechanism is also known to reduce torque servo-control bandwidth and to separate link-side dynamics from actuator…
We propose a scheme that uses the signal strength received from commercial RF sensors to determine the position of a sensor underwater. The scheme can give accurate position information and has fast update rate, but is limited to short sensor range with the signal identification problem. The infrast…