34 accepted papers
In this paper, we propose a Contact Diffusion Model (CDM), a novel learning-based approach for multi-contact point localization. We consider a robot equipped with joint torque sensors and a force/torque sensor at the base. By leveraging a diffusion model, CDM addresses the singularity where multiple
Designing effective reward functions remains a fundamental challenge in reinforcement learning (RL), as it often requires extensive human effort and domain expertise. While RL from human feedback has been successful in aligning agents with human intent, acquiring high-quality feedback is costly and…
Disturbance observer (DOB) is a well-known two-loop control structure that imparts robustness to a controller with a simple implementation. As a nonlinear DOB for the robotic systems, we proposed so-called nonlinear robust internal-loop compensator (NRIC) framework in our previous work. In this pape…
This paper proposes a novel design framework for a fully actuated drone with non-isotropic wrench shape. Conventional fully actuated drones face challenges related to high energy consumption during aerial contact manipulation, particularly when force exertion along a specific direction is required.…
While robust model predictive control (MPC) has been studied extensively in recent decades, addressing unmatched disturbances in underactuated robotic systems is still challenging. In this paper, we propose a method to enhance the robustness of the MPC through the online estimation of disturbances u…
We aim to solve the problem of data-driven collision-distance estimation given 3-dimensional (3D) geometries. Conventional algorithms suffer from low accuracy due to their reliance on limited representations, such as point clouds. In contrast, our previous graph-based model, GraphDistNet, achieves h…
In this paper, we propose a model predictive control (MPC) that accomplishes interactive robotic tasks, in which multiple contacts may occur at unknown locations. To address such scenarios, we made an explicit contact feedback loop in the MPC framework. An algorithm called Multi-Contact Particle Fil…
This paper presents a novel algorithm for robot task and motion planning (TAMP) problems by utilizing a reachability tree. While tree-based algorithms are known for their speed and simplicity in motion planning (MP), they are not well-suited for TAMP problems that involve both abstracted and geometr…
During operation, aerial manipulation systems are affected by various disturbances. Among them is a gravitational torque caused by the weight of the robotic arm. Common propeller-based actuation is ineffective against such disturbances because of possible overheating and high power consumption. To o…
This paper proposes a decentralized passive impedance control scheme for collaborative grasping using under-actuated aerial manipulators (AMs). The AM system is formulated, using a proper coordinate transformation, as an inertially decoupled dynamics with which a passivity-based control design is co…
In this paper, we propose an algorithm that estimates contact point and force simultaneously. We consider a collaborative robot equipped with proprioceptive sensors, in particular, joint torque sensors (JTSs) and a base force/torque (F/T) sensor. The proposed method has the following advan-tages. Fi…
Alginate hydrogels are widely researched in phar-maceutical applications for their abilities to encapsulate and dis-perse therapeutics in response to stimuli. While effective, their utility can be greatly improved once converted into artificial cell soft-microrobots, allowing them to actively naviga…
This paper proposes a parameterization method to represent SO (3) over multiple turns. This method is called a memory-based parameterization, because the idea is to integrate the past trajectory of exponential coordinates. The parameterization is consistent in the sense that the true rotation matrix…
This paper presents an adaptive backstepping controller for the reference tracking of an alginate artificial cell. An adaptive controller was implemented to precisely manipulate a magnetic artificial cell actuated by rotating magnetic fields. The rolling motion of a small-scale robot in a fluidic en…
Untethered mobile microrobots controlled by an external magnetic gradient field can be employed as advanced biomedical applications inside the human body such as cell therapy, micromanipulation, and noninvasive surgery. Haptic technology and telecommunication, on the other hand, can extend the poten
Aerial robotic manipulation is an emergent trend that poses several challenges. To overcome some of these, the DLR cable-Suspended Aerial Manipulator (SAM) has been envisioned. SAM is composed of a fully actuated multi-rotor anchored to a main carrier through a cable and a KUKA LWR attached below th…
The modular assembly and actuation of 3D printed milliscale cuboid robots using a globally applied magnetic field is presented. Cuboids are composed of a rectangular resin shell embedded with two spherical permanent magnets that can independently align with any applied magnetic field. Placing cuboid…
This paper presents a design of oscillation damping control for the cable-Suspended Aerial Manipulator (SAM). The SAM is modeled as a double pendulum, and it can generate a body wrench as a control action. The main challenge is the fact that there is only one onboard IMU sensor which does not provid…
This paper presents scalable designs and fabrication, actuation, and manipulation techniques for soft millirobots under uniform magnetic field control. The millirobots were fabricated through an economic and robust moulding technique using polydimethylsiloxane (PDMS), acrylonitrile butadiene styrene…
This paper presents a novel telepresence system for enhancing aerial manipulation capabilities. It involves not only a haptic device, but also a virtual reality that provides a 3D visual feedback to a remotely-located teleoperator in real-time. We achieve this by utilizing onboard visual and inertia…
This article discusses the design, modeling, and application of a powerful hexapole magnetic tweezer system for closed-loop 3D swarm control applications. The system consists of six sharp tapered magnetic poles that are integrated with six electromagnetic coils and mounted on two yokes composed of 3
High risk of a collision between rotor blades and the obstacles in a complex environment imposes restrictions on the aerial manipulators. To solve this issue, a novel system cable-Suspended Aerial Manipulator (SAM) is presented in this paper. Instead of attaching a robotic manipulator directly to an…
This paper presents 2D feedback control and open loop 3D trajectories of heterogeneous chemically catalyzing Janus particles. Self-actuated particles have enormous implications for both in vivo and in vitro environments, which make them a diverse resource for a variety of medical and assembly applic…
Stability is not trivial in aerial manipulation tasks because of the dynamical coupling between the aerial vehicle and the manipulator. This is especially true when the manipulator becomes heavy, so that its dynamics can be significant. In this letter, a stabilizing controller for the regulation of
This paper presents a passive compliance control for aerial manipulators to achieve stable environmental interactions. The main challenge is the absence of actuation along body-planar directions of the aerial vehicle which might be required during the interaction to preserve passivity. The controlle…
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…
This paper presents that the joint torque control capability can be enhanced by adding physical damper to a series elastic actuator (SEA). Joint torque tracking of standard SEA has known limitations that the torque dynamics has an relative order of two, and, as a consequence, the torque controller o…
We present fundamental progress on parallel self-assembly using large swarms of microscale particles in complex environments, controlled not by individual navigation, but by a uniform, global, external force with the same effect on each particle. Consider a 2-D grid world, in which all obstacles and
Microrobots have great potential for microassembly and non-invasive surgery applications. Motivated by studies proposing MRI-guided drug delivery to tumor cells using magnetic micro carriers, this paper studies two major challenges of this problem: (i) microrobot swarm trajectory generation, and (ii…
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…
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…
This paper investigates the use of single control signal (magnetic field direction) and PSO-MPC algorithm to control multiple magnetized Tetrahymena pyriformis (T. pyriformis) cells to move from their initial positions to their target positions simultaneously while avoiding the obstacle. The magneti…
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…
As microscale robots are becoming increasingly popular due to their potential for medical and industrial applications, various designs of microscale robotic system have been developed. However, there has not been much work on autonomous control algorithms for microscale robots in microfluidic enviro…