Akiya Kamimura

This article introduces a dimension-decomposed geometric learning framework called Sliced Learning for disturbance identification in quadrotor geometric attitude control. Instead of conventional learning-from-states, this framework adopts a learning-from-error strategy by using the Lie-algebraic error representation as the input feature, enabling axiswise space-decomposition (“slicing”) while preserving the SO(3) structure. This is highly consistent with the geometric mechanism of cognitive control observed in neuroscience, where neural systems organize adaptive representations within structured subspaces to enable cognitive flexibility and efficiency. Based on this framework, we develop a lightweight and structurally interpretable Sliced Adaptive-Neuro Mapping module. The high-dimensional mapping for online identification is axially “sliced” into multiple low-dimensional submappings (“slices”), implemented by shallow neural networks and adaptive laws. These neural networks and adaptive laws are updated online via Lyapunov-based adaptation within their respective shared subspaces. To enhance interpretability, we prove exponential convergence despite time-varying disturbances and inertia uncertainties. To the best of the authors' knowledge, sliced learning is among the first frameworks to demonstrate lightweight online neural adaptation at 400 Hz on resource-constrained microcontroller units, such as STM32, with real-world experimental validation.

An emerging application of microfluidic and pneumatic logic in soft robotics is the selective access to tethered pneumatic elements through a reduced number of pneumatic lines (i.e., addressing). In our previous work, we demonstrated two binary addressing systems based on sequences of pressure pulses transmitted in parallel through the same lines later used to actuate the selected elements. This approach supports distributed architectures, parallel actuation, and unlimited addresses, albeit at the cost of longer and complex addressing processes. In this work, we present multi-pressure addressing systems, which solve the primary limitation of binary designs (pressure spikes upon connection of the actuators) and are compatible with multi-pressure components like hysteretic or sequence valves. We also present a strategy for linear networks that maximizes the number of addresses for a given sequence length. We validate our designs with three physical prototypes: a hierarchical module that controls a pneumatic robotic arm, demonstrating the smooth connection of the actuators; a non-hierarchical module with a sequence valve, that triples the network addresses compared to its binary-pressure version (36 addresses, each with 4 simultaneous outputs, using 5 lines); and a linear network with 18 distributed logic modules and air reservoirs emulating adjustable distances, used to evaluate transient pressure drops over extended lengths and to validate the proposed shortened addressing strategy (19 addresses of four or fewer pressure pulses, each with 4 simultaneous outputs, using 5 lines extended up to 1900 m).

In this paper, we present a VR-based control framework for multi-UAV (rotorcraft-type) aerial manipulation that enables simultaneous control of each UAV and its onboard five-degree-of-freedom (5-DoF) manipulator using virtual-reality controllers. Instead of relying on dense button mappings or predefined gestures, the framework maps natural VR-controller motions in real time to vehicle pose and arm joint commands. The UAVs respond smoothly to translational and rotational inputs, while the manipulators accurately replicate dexterous hand motions for precise grasping. Beyond single-platform operation, we extend the framework to cooperative dual-UAV manipulation, leveraging two-hand poses captured via VR controllers to coordinate two UAV-arm systems for payload transportation and obstacle traversal. Simulation experiments demonstrate accurate trajectory tracking and the potential for successful cooperative transport in cluttered environments, indicating the framework’s suitability for telemanipulation, search-and-rescue, and industrial tasks.

This study proposes a concept for on-demand manufacturing of soft mechanisms using laser technology for welding and cutting plastic sheets. Soft mechanisms, which are known for their flexibility, compliance, and lightweight properties, have been explored in various fields. Despite advancements in soft robotics, challenges such as lengthy production times, complex fabrication processes, and reliance on specialized expertise persist. Laser processing is a prominent technique for the fabrication of soft mechanisms, particularly film-based mechanisms, in terms of production time and manufacturability. Such methodologies are considered innovative; however, they remain underexplored. This study advances laser methodology by introducing a novel on-demand production approach that leverages laser-based techniques to fabricate multilayered soft mechanisms from plastic sheet materials. The feasibility of this concept, applicable to both small and large mechanisms, was validated using a commercial laser-cutting machine. We successfully fabricated a range of soft mechanisms, including a peristaltic robot capable of moving at 3.3 mm/s while carrying a load of 1.2 kg, and a stackable valve mechanism that switches flow paths using a plastic leaf spring and an inflatable airbag, both constructed from multiple plastic sheets. Key contributions of this study include the development of innovative fabrication protocols for soft mechanisms and multiple examples demonstrating the versatility of the technique. This study advances the field of soft robotics by providing a practical and efficient solution for manufacturing complex, large-scale soft robots with potential applications in space exploration, industrial automation, and other unstructured environments.

Our method enables interpretable online identification and robust disturbance rejection for centralized multi-quadrotor transportation under model uncertainties and time-varying disturbances.

Typical soft actuators can perform unidirectional bending between pressurized and loose states. Multidirectional motion commonly requires multiple chambers or the bundling of multiple unidirectional actuators. If multidirectional motion can be achieved with a simple mechanism, it will provide considerable flexibility in designing objects such as grippers or wearable devices. Here, we present a new design for a multidirectional soft actuator that uses a combination of a temperature-sensitive material (TSM) and a non-temperature-sensitive material (NTSM). The actuator consists of a fluid chamber, and the bending is controlled by the temperature and pressure of the working fluid to balance the stiffness between the TSM and NTSM. In this study, the concept, design, and fabrication method are introduced, and the basic characteristics are discussed through experiments and modeling using a prototype actuator. The results of the static analysis of the curvature and curve fitting based on the model show that actuator bending in a static state can be represented by a simple linear-spring model. We also discuss the features, potential, and applications of the actuator by demonstrating its grasping capabilities.

The demand for payload transportation has shown exceptional growth owing to its inherent convenience and ability to reduce manpower requirements. To address the limitations of previous studies that primarily employed a single multi-rotor to deploy payloads within a limited reach, we designed a cable-suspended aerial payload deployment system with a large workspace that allowed payload deployment at a distance from the multi-rotor platforms. Our system comprised two multi-rotors, a payload deployment device (PDD, hereafter) with ducted fans, servomotors and a microcomputer. The ducted fans were used not only for swing suppression during payload transportation, but also to ensure that the PDD maintained a certain angle to the vertical plane where the dual multi-rotors were located during the deployment phase. Compared to existing research results, our design has a larger working distance in the vertical and horizontal directions. The controller designed for the PDD was adaptive and robust to variation of the payload mass and distance between the dual multi-rotors. We verified the effectiveness of our design and algorithms through several experiments.

Quadcopter is a type of unmanned aerial vehicle (UAV) that offers excellent flight ability albeit with relatively low payload. Despite its widespread use for transportation, improving its robustness against disturbances and carrying capacity has been challenging. Thus, this study proposed a cable suspended multi-UAVs transportation system with a controller and disturbance observer that is highly robust against disturbances. The primary objective of this study is to design a robust controller and disturbance observer by considering the effect of the cable-suspended payload on the UAV as a part of the disturbance. Consequently, reducing the complexity of the problem and allowing a range of algorithms to be used. A controller and disturbance observer are designed based on backstepping control and the extended state of the model, respectively, to control the flight of the multiple UAVs while carrying a cable-suspended payload. Further, to exploit the agility of quadcopters and avoid obstacles, a virtual structure based leader-follower dynamic formation scheme is introduced to change the formation geometry during the flight with cable suspended payload. This scheme does not make any assumption regarding the status of cable tension during the flight and thus no feedback measurement is required from payload. Moreover, the stability analysis of the proposed system is verified theoretically based on Lyapunov stability and through indoor experiments.

Conventional inspection procedures using industrial endoscope cameras find it challenging to inspect narrow pipes because the endoscope cannot be inserted in the pipes due to the increasing friction and complex pipe structure. Active propulsion techniques can help improve inspection efficiency; however, the locomotion mechanism in such a narrow space is challenging because of the pipe’s geometrical configuration. In this study, a novel flexible propulsion module is proposed for narrow pipe inspection. The module is designed based on a newly proposed hollow-type duplex-chambered inchworm mechanism, which achieves smooth inchworm locomotion using only two air supply lines. With a simple attachable module design, the inspection operator can easily add active propulsion capabilities onto the regular industrial endoscope camera with a maximum diameter of 7 mm. The concept of the system and the structure of the mechanism are presented herein. Various experiments and simulations were performed to reveal the characteristics of the mechanism, and the results are discussed in terms of operating pressure, generated force, and locomotion speed, among other parameters. A prototype demonstrated smooth locomotion through 31-mm pipes at 26.6, 22.1, and 51.1 mm/s for horizontal locomotion, vertical climbing, and vertical descent, respectively, and performed well through a bending pipe.

Until the 1970s, hydraulic actuators were widely used in many mechanical systems; however, recently, electric motors have become mainstream by virtue of their improved performance, and hydraulic motors have largely been replaced by electric motors in many applications. Although this trend is expected to continue into the future, it is important to comprehensively evaluate which motor is most suitable when designing mechanical systems. This paper presents the results of a survey of the performance of electric and hydraulic servo motors and aims to provide quantitative data that can be used as a reference for selecting appropriate motors. We surveyed AC, AC direct, brushless DC, and brushed DC electric motors and swash plate-type axial piston, bent axis-type axial piston, crank-type radial piston, and multistroke-type radial piston hydraulic motors. Performance data were collected from catalogs and nonpublic data. We compared and evaluated the characteristics of these diverse servo motors using indexes such as torque, rotating speed, output power, power density, and power rate.