Pakpong Chirarattananon

Monopedal hopping robots offer exceptional mobility over discontinuous terrain but require consistent foot‐ground contact to maintain stance‐phase dynamics and prevent instability. This work presents a lightweight, compliant footpad that enhances the terrain adaptability of a hopping robot. The design combines a planar foot supported by a compliant spherical joint for self‐alignment with embedded spines to improve traction on uneven or slippery surfaces. Controlled drop tests demonstrate that the footpad preserves stance‐phase dynamics while reducing slipping and entrapment across rigid, granular, and soft terrains. Indoor trajectory tracking and outdoor experiments validate reliable hopping on grass, rocky trails, sand, and frozen ground, demonstrating that a simple yet effective compliant‐spined design can significantly expand the operational envelope of hopping robots in unstructured environments.

Improving the adaptability and versatility of micro aerial robots is crucial for expanding their application range. In this paper, we present a transformable tethered aerial platform composed of two bicopters tethered together with a cable, which is capable of mid-air transitions and robot-environment physical interactions. The platform can operate in three modes: free-flight mode, tethered-flight mode, and quadcopter mode. These modes are enabled by changing the tension and length of the cable, without the need for additional reconfiguration mechanisms. To fully exploit the capabilities of the proposed system, we derive the dynamic model of the platform and develop the control methods for each mode. The developed controller ensures stable flight in each mode and also enables the platform to operate with limited position feedback. We validate the feasibility of the transformable design through a series of experiments, demonstrating stable transitions between modes and effective physical interactions. Notably, by using the cable as an end effector, the platform can exert forces and torques on the environment through cable tension, eliminating the need for extra grippers or actuators and showcasing the versatility of the system in real-world tasks.

While many animals exhibit impressive hopping capabilities, machines have struggled to match their performance. Current hopping robots face limitations in power density, energy efficiency, and control stability. Here, we present a parallel-elastic actuation mechanism with a reactive latch that optimizes energy transfer, enabling a legged robot to achieve hopping heights and continuity previously unattainable. This mechanism efficiently stores and releases energy, extending the actuation period over the aerial phase while minimizing stance time. Our robot achieves a maximum hopping height of 3.6 meters, surpassing both human and animal records while demonstrating sustained, high-frequency hopping cycles with minimal power requirement. By integrating inertia-based onboard sensorimotor autonomy, we demonstrate stable, controlled hopping in environments without external aid. These results represent a step toward bridging the performance gap between biological and robotic locomotion, with potential to influence the design of future legged systems.

With the ubiquitous deployment of drones in various fields, aircraft capable of both hovering and forward flight have garnered increasing attention due to their versatility and long-range cruising capability. Currently, these multimodal aerial vehicles are generally achieved by introducing additional actuators, which inevitably results in redundant mass, complex structures, and reduced flight efficiency. In this work, we propose a 39-g bimodal aerial robot equipped with only two propellers as actuators. The robot can cruise like a fixed-wing aircraft or hover in place through self revolving. The transition between its flight modes is achieved through the introduction of several passive morphing mechanisms and aerodynamically bistable structure. With only two rotors, the robot leverages aerodynamic loads on the wings to maintain its flight configuration. Strategic adjustment of propeller thrust enables seamless transition between forward flight and hovering modes. Extensive indoor and outdoor experiments demonstrate the robot’s stable operation in both flight modes, with power loading of 10.24 g/W in forward flight and 7.11 g/W in hovering mode. The robot successfully performs mode transitions in a predictable and repeatable manner. This approach enables a structurally proficient solution for multimodal flight without the need for additional actuators.

Mobile robots have revolutionized various fields, offering solutions for manipulation, environmental monitoring, and exploration. However, payload capacity remains a limitation. This paper presents a novel thrust-based robotic hopper capable of carrying payloads up to 9 times its own weight while maintaining agile mobility over less structured terrain. The 220 gram robot carries up to 2 kg while hopping—–a capability that bridges the gap between high-payload ground robots and agile aerial platforms. Key advancements that enable this high-payload capacity include the integration of bidirectional thrusters, allowing for both upward and downward thrust generation to enhance energy management while hopping. Additionally, we present a refined model of dynamics that accounts for heavy payload conditions, particularly for large jumps. To address the increased computational demands, we employ a neural network compression technique, ensuring real-time onboard control. The robot's capabilities are demonstrated through a series of experiments, including leaping over a high obstacle, executing sharp turns with large steps, as well as performing simple autonomous navigation while carrying a 730 g LiDAR payload. This showcases the robot's potential for applications such as mobile sensing and mapping in challenging environments.

Directional filtering has been applied to distinguish between the ascending and descending flows in functional ultrasound imaging, however, it can lead to incorrect measurement of the flow speed and direction when using the directional filtering-based color Doppler ultrasound velocimetry (iCD_US). Specifically, in cases where the frequency spectrum bandwidth of a unidirectional flow extends into both negative and positive frequency domains, directional filtering may erroneously produce bidirectional velocities. Here, we propose an adaptive color Doppler ultrasound technique (aCD_US), which addresses this issue by analyzing the envelope of the Doppler spectrum and then adaptively using the whole spectrum integration or directional filtering-based approach to estimate the flow velocity. The proposed aCD_US was validated through numerical simulations and phantom experiments under various flow conditions, demonstrating superior performance in estimating axial velocities of unidirectional, bidirectional, and horizontal flows. Notably, numerical simulations showed that aCD_US achieved over 90% directional accuracy and less than 15% velocity deviation at signal-to-noise ratios larger than -1 dB. In vivo experiments on mouse cerebral blood flow further highlighted its advantages, with aCD_US surpassing conventional color Doppler velocimetry and iCD_US in reconstructing axial flow velocity maps. The quantitative comparison between aCD_US and vULM shows a strong overall correlation in their axial velocity measurements, with a Pearson correlation coefficient of 0.760 (p = 0.000). These results demonstrate the advantage of aCD_US in precise microvessel networks velocity quantification and its potential to advance microvascular imaging accuracy in both research and clinical applications.

Investigations into animal locomotion across diverse environments have highlighted the universal applicability of adjustable reciprocal motion, offering insights into simplifying actuation systems for multi-modal robots. However, achieving unified and efficient reciprocal motion with environmental adaptability in miniature robotic systems is challenging due to constraints of size, weight, and the need for controlled degree of freedom. Here, we present the UniCore, a miniature unified actuation platform capable of flying, swimming, and running with modular appendages. This platform features bio-inspired motor-spring resonance actuation systems, with a central controller that generates four adjustable reciprocal control signals based on a central pattern generator model. Performance validation demonstrates UniCore’s proficiency in achieving three distinct modes of locomotion, underscoring the effectiveness of reciprocal motion for the locomotion of both animals and machines. All in all, this work demonstrates the potential of a unified reciprocal actuation platform to eliminate morphological and actuation redundancies commonly found in existing multi-modal robots, paving the way for more efficient and versatile miniature robotic systems.

Insect-scale robots face two major locomotive challenges: constrained energetics and large obstacles that far exceed their size. Terrestrial locomotion is efficient yet mostly limited to flat surfaces. In contrast, flight is versatile for overcoming obstacles but requires high power to stay aloft. Here, we present a hopping design that combines a subgram flapping-wing robot with a telescopic leg. Our robot can hop continuously while controlling jump height and frequency in the range of 1.5 to 20 centimeters and 2 to 8.4 hertz. The robot can follow positional set points, overcome tall obstacles, and traverse challenging surfaces. It can also hop on a dynamically rotating plane, recover from strong collisions, and perform somersaults. Compared to flight, this design reduces power consumption by 64 percent and increases payload by 10 times. Although the robot relies on offboard power and control, the substantial payload and efficiency improvement open opportunities for future study on autonomous locomotion.

Rigid robots can achieve precise motions but expose shortcomings in system complexity, fabrication cost, and human–robot interaction, which motivates researchers to develop various soft robots to fill these gaps. Electro-hydraulic actuators (EHAs) have received widespread attention and been used in many soft robots due to impressive high-strain, fast-speed, and rapid-response characteristics. However, existing EHAs face challenges in achieving large-deformation, high-robustness, and low-weight simultaneously. This limits the application of EHAs in robotic systems that are weight-sensitive or require fail-safe and fault-tolerant behavior. Here, we present a lightweight (0.98 g) electro-pneumatic actuator (EPA) filled with air and only 0.1-mL liquid dielectric, which achieves high-speed bending from 11° to 93.5° in 60 ms, large-angle bending from 11° to 104° in 2 s (the largest in current EHAs), and high-frequency swing at 20 Hz. The EPA is ultrarobust and can operate properly after being punctured by four needles or crushed twice by a 1500-kg vehicle. Furthermore, to validate the above features of EPAs, three applications are demonstrated at a voltage of 6 kV, including four-finger grippers, fast-crawling robots, and water-walking robots. This work pushes the boundaries of robustness and lightweight for EHAs, providing a foundation for the application of electro-pneumatic actuation in soft robotics.

We present a hybrid aerial-ground robot that combines the versatility of a quadcopter with enhanced terrestrial mobility. The vehicle features a passive, reconfigurable single wheeled leg, enabling seamless transitions between flight and two ground modes: a stable stance and a dynamic cruising configuration. The cruising mode exhibits exceptional turning performance, achieving a centrifugal acceleration of 0.55$g$, over 30% higher than previous records, due to an inherent yaw stabilization effect. This mechanism also reduces control effort and enhances roll stability, enabling reliable navigation on irregular surfaces. While this passive design achieves structural simplicity, it trades off power efficiency for enhanced maneuverability. We provide a comprehensive analysis of the system's dynamics and experimentally demonstrate agile movements across various scenarios.