Search Results (83)

The aerial acrobat robot is a mechanical structure that achieves continuous acrobatic motion without electrical power by utilizing gravitational potential energy.The power of this motion is the rotational motion resulting from the imbalance of moments caused by both the masses, called counterbalance, and the weight of the robot. Or, it is the rotational motion resulting from the reciprocal energy conversion between the gravitational potential and kinetic energy of these two masses. Using the quasi-static single-link model mechanism, we derived a formula for the power moment that is important in the design of the mechanical structure to produce the aerial acrobat robot’s motion. This structure is mainly made of resin and is approximately 2 m long. Based on this structure, we developed a paper craft aerial acrobat robot compacted to about 0.27 m so that anyone can easily play with it. In the paper craft aerial acrobat robot based on the quasi-static single-link model, instability in the rotational behavior becomes apparent. To enhance the accuracy of the analysis of rotational moments, which are crucial in design, we develop a modeling method for a paper craft aerial acrobat robot using multibody dynamics. Furthermore, the theoretical solution for a simplified model of the paper craft aerial acrobat robot is constructed based on the double pendulum. The dynamic moments obtained by the modeling method of the paper craft aerial acrobat robot is verified by comparing the theoretical solution. Full article

This paper proposes a Takagi–Sugeno–Kang Elliptic Type-2 Fuzzy Brain-Imitated Neural Network (TET2FNN)-based decoupling control strategy for nonlinear underactuated mechanical systems subject to uncertainties. A sliding-mode framework is employed to construct a decoupled control architecture, in which an intermediate variable is introduced to separate two second-order sliding surfaces, thereby forming a decoupled slip surface. The TET2FNN acts as the main controller and approximates the ideal control law online, while a robust compensator is incorporated to suppress approximation errors and guarantee closed-loop stability. Simulation studies conducted on a double inverted pendulum system demonstrate that the proposed method achieves improved tracking accuracy and disturbance rejection compared with representative state-of-the-art controllers. Furthermore, the computational burden remains reasonable, indicating that the proposed scheme is suitable for real-time implementation and practical nonlinear control applications. Full article

Step length is a fundamental parameter for gait assessment, reflecting complex neuromuscular and biomechanical behavior. Accurate step-length estimation is clinically relevant for monitoring populations with neurological or musculoskeletal conditions, as well as older adults. This study presents a novel biomechanical model, inspired by the inverted double pendulum, for step-length estimation under asymmetric gait conditions using a single inertial sensor on the lower back. Unlike models that assume symmetry, the proposed model explicitly incorporates pelvic rotation, enabling more accurate step length estimation, particularly in individuals with gait impairment. The model was validated against a gold standard OptiTrack^® (Corvallis, OR, USA) system with 33 adults: 21 participants without and 12 with gait impairment. Results show that the model achieved low Median Absolute Errors (MdAE), below 0.04 m in participants without gait impairment and remaining within 0.06 m in those with impairment. Statistical validation confirmed a strong correlation with the reference system (R = 0.96, R² = 0.93) and a clinically trivial mean bias (0.64 cm) from Bland-Altman analysis. These results validate the model’s effectiveness under various gait conditions, suggesting its technical feasibility and strong potential for clinical and real-world applications, particularly for the longitudinal monitoring of patients with functional impairments. Full article

The article presents a numerical analysis of a nonlinear seven-degree-of-freedom mechanical system composed of stick–slip-driven masses and magnetically coupled pendulums, emphasizing the influence of friction and magnetic coupling on the system’s dynamics. The objective is to develop a dynamic model, analyze bifurcation structures and synchronization, and examine multistability and sensitivity to initial conditions. The equations of motion are derived using the Lagrangian formalism and expressed in a dimensionless form. Bifurcation diagrams, phase portraits, spectral diagrams, and attraction basins are used to explore system behavior across parameter ranges. Saddle-node, Neimark–Sacker, and period-doubling bifurcations are observed, along with multiple coexisting attractors—periodic, quasiperiodic, and chaotic—indicating pronounced multistability. Small variations in initial conditions or system parameters lead to abrupt transitions between attractors. It has been shown that the mass of the pendulum strongly affects the system’s synchronization capability. Full article

A wheeled–legged robot has the advantage of stable and agile movement on flat ground and an excellent ability to overcome obstacles. However, when faced with a narrow footprint, there is a limit to its ability to move. We developed the control moment gyroscope (CMG) unicycle–legged robot to solve this problem. A scissored pair of CMGs was applied to control the roll balance, and the pitch balance was modeled as a double-inverted pendulum. We performed Linear Quadratic Regulator (LQR) control and model predictive control (MPC) in a system in which the control systems in the roll and pitch directions were separated. We also devised a method for controlling the rotation of the robot in the yaw direction using torque generated by the CMG, and the performance of these controllers was verified in the Gazebo simulator. In addition, forward driving control was performed to verify mobility, which is the main advantage of the wheeled–legged robot; it was confirmed that this control enabled the robot to pass through a narrow space of 0.15 m. Before implementing the verified controllers in the real world, we built a CMG test platform and confirmed that balancing control was maintained within $\pm 1^{\circ }$. Full article

Underactuated systems, such as rotary and double inverted pendulums, challenge traditional control due to nonlinear dynamics and limited actuation. Classical methods like state-feedback and Linear Quadratic Regulators (LQRs) are commonly used but often require high gains, leading to excessive control effort, poor energy efficiency, and reduced robustness. This article proposes a generalized state-feedback controller with its own internal dynamics, offering greater design flexibility. To automate tuning and avoid manual calibration, we apply Bayesian Optimization (BO), a data-efficient strategy for optimizing closed-loop performance. The proposed method is evaluated on two benchmark underactuated systems, including one in simulation and one in a physical setup. Compared with standard LQR designs, the BO-tuned state-feedback controller achieves a reduction of approximately 20% in control signal amplitude while maintaining comparable settling times. These results highlight the advantages of combining model-based control with automatic hyperparameter optimization, achieving efficient regulation of underactuated systems without increasing design complexity. Full article

The control of a biped robot is a challenging task due to the hard-to-stabilize dynamics. Generating a suitable walking reference trajectory is a key aspect of this problem. This article proposes a novel method of generating walking patterns for biped robots. The method integrates the double support phase and the single support phase into one step, and uses this step as the unit for trajectory generation through quadratic optimization with terminal constraints based on the Linear Inverted Pendulum Model, enabling us to shorten the optimization horizon while still generating natural walking trajectories. Moreover, by restricting the position and acceleration of the center of mass (COM) in the vertical direction, an excessive constraint is formed on the Zero Moment Point (ZMP) to offset the nonlinear effects of the COM’s vertical motion on the ZMP. This allows the COM of the robot to change in the vertical direction while maintaining the linearity of the optimization problem. Finally, the performance of the proposed method is validated by simulations and experiments of walking on flat ground and stairs using a position-controlled biped robot, Neubot. Full article

In this study, we propose a novel asymmetric high-performance MEMS pendulum accelerometer comprising a sensitive structure and an interface circuit. The sensitive structure, designed with asymmetric mass blocks, significantly improves both sensitivity and structural stability. The sensor is fabricated using a double-side polished (100) N-type silicon wafer and its structure is ultimately realized through ICP (Inductively Coupled Plasma) etching. We also develop and fabricate the corresponding interface circuit. The accelerometer is evaluated through a static field roll-over test, demonstrating excellent performance with a sensitivity of 1.247 V/g and a nonlinearity of 0.8% within the measurement range of −2 g to 2 g. Full article

Toward the innovative design of tunable structures for energy generation, this paper presents an extended Floating Frame of Reference (FFR) formulation capable of modeling slope discontinuities in flexible multibody systems—overcoming a key limitation of conventional FFR methods that assume slope continuity. The model is validated using a spatial double-pendulum structure composed of circular beam elements, representative of out-of-plane energy harvesting systems. To investigate the influence of boundary constraints on dynamic behavior, three electromagnetic clamping configurations—Fixed–Free–Free (XFF), Fixed–Free–Fixed (XFX), and Free–Fixed–Free (FXF)—are implemented. Tri-axial accelerometer measurements are analyzed via Fast Fourier Transform (FFT), revealing natural frequencies spanning from 38.87 Hz (lower frequency range) to 149.01 Hz (higher frequency range). For the lower frequency range, the FFR results (38.76 Hz) show a close match with the experimental prediction (38.87 Hz) and ANSYS simulation (36.49 Hz), yielding 0.28% error between FFR and experiments and 5.85% between FFR and ANSYS. For the higher frequency range, the FFR model (148.17 Hz) achieves 0.56% error with experiments (149.01 Hz) and 0.85% with ANSYS (146.91 Hz). These high correlation percentages validate the robustness and accuracy of the proposed FFR formulation. The study further shows that altering boundary conditions enables effective frequency tuning in discontinuous structures—an essential feature for the optimization of application-specific systems such as wave energy converters. This validated framework offers a versatile and reliable tool for the design of vibration-sensitive devices with geometric discontinuities. Full article

This paper presents a novel dynamic modeling framework for gantry crane systems based on the cart double pendulum with dual cables (CDPD) model. The CDPD model systematically incorporates the effects of dual suspension cables, equalizer beams, and closed-chain kinematic constraints, enabling an accurate simulation of both symmetric and asymmetric lifting scenarios. Utilizing Kane’s method, the model efficiently handles redundant coordinates and holonomic constraints, resulting in a compact and numerically robust formulation. Validation results demonstrate strict energy conservation and consistency with traditional models in limiting cases. The proposed approach provides a unified and extensible foundation for the advanced analysis, control, and optimization of large-scale gantry crane operations. Full article

Gantry cranes play a pivotal role in industrial production. Gantry cranes exhibit clear double-swing characteristics in actual working conditions, complicating anti-swing control. Most existing anti-swing control methods are based on a simplified single-pendulum model. The present paper puts forward a double-pendulum model for gantry cranes and proposes an adaptive hierarchical sliding mode control based on a neural network according to the actual working conditions. The use of a neural network and adaptive layered sliding mode control can effectively inhibit chattering, thus improving control performance and stability and achieving the goal of anti-shaking control, thus effectively inhibiting residual oscillation. This method has been demonstrated to be effective in achieving the objective of anti-shudder control, thereby effectively suppressing residual oscillation. Compared with hierarchical sliding mode control, the proposed method reduces the maximum residual oscillation angle of the hook and payload by approximately 80%. In comparison with the conventional sliding mode control, the maximum residual oscillation angle is reduced by approximately 84%. Furthermore, the control force amplitude is reduced to 5.23 N, representing decreases of 30.2% and 37.4%, respectively. These comparative results demonstrate the superior oscillation suppression. The system also shows a reliable performance against potential disturbances. Full article

In this paper, we investigate the nonlinear dynamic behavior of a cart–double pendulum system with single time delay feedback control. Based on the center manifold theorem and stochastic averaging method, a reduced-order dynamic model of the system is established, with a focus on analyzing the influence of time delay parameters and stochastic excitation on the system’s Hopf bifurcation characteristics. By introducing stochastic differential equation theory, the system is transformed into the form of an Itô equation, revealing bifurcation phenomena in the parameter space. Numerical simulation results demonstrate that decreasing the time delay and increasing the time delay feedback gain can effectively enhance system stability, whereas increasing the time delay and decreasing the time delay feedback gain significantly improves dynamic performance. Additionally, it is observed that Gaussian white noise intensity modulates the bifurcation threshold. This study provides a novel theoretical framework for the stochastic stability analysis of time delay-controlled multibody systems and offers a theoretical basis for subsequent research. Full article

A collaborative inter-laboratory study was conducted to characterise the performance of the novel 250 W External Discharge Plasma Thruster (XPT) with a channel-less Hall effect-type thruster designed to address lifetime limitations and lower-power efficiency challenges in conventional Hall effect thrusters. This study aimed to validate performance measurements across different facilities and thrust stands, investigating potential facility effects on thrust characterisation. Performance testing was conducted both at the University of Surrey using a torsional thrust balance and at the University of Southampton with a double inverted pendulum thrust stand, providing independent verification of the thrust and efficiency metrics. The comparison highlighted the importance of cross-facility testing with differing background pressures, calibration methods, and thrust balance types. These differences provide valuable insights, ensuring more robust and reliable low-power thruster characterisation. The XPT thruster demonstrated consistent performance across both the University of Surrey and University of Southampton facilities, with thrust levels ranging from 1.60 mN to 11.8 mN, specific impulses from 327 s to 1067 s, and anode efficiencies up to 11%. Higher anode voltages and mass fluxes at Southampton enabled extended operational envelopes, revealing performance plateaus at elevated powers, particularly for flow rates above 8 sccm. Cross-facility testing highlighted facility-dependent influences, with Southampton achieving a higher thrust and specific impulse at lower flow rates (5–6 sccm) due to increased anode currents, while discrepancies between test sites of up to 25% were observed at higher flow rates (8–10 sccm) and powers above 200 W. Characterisation identified an optimal operating range at 200 W of anode power with a mass flux below 8 sccm. This work underscores the importance of inter-laboratory validation in electric propulsion testing and provides insights into the best practices for assessing next-generation Hall effect-type thrusters. Full article

Based on the single-crank linkage mechanism and the double-pendulum rod mechanism, herein, a reciprocating swing single-blade cutting device is appropriately designed for the needs of GLVs’ planting and cutting operations. It can effectively solve the existing double-blade cutting device’s in-soil operation issue, where clods of soil and stones adhere to the upper and lower cutting blades, resulting in problems such as excessive wear and blade fracture. Using ADAMS, a virtual model of the cutting device is established, and a kinematic analysis of the cutting process is performed to accurately determine the cutting trajectory curve and the mathematical model of the cutting rate. The single-factor test and quadratic regression orthogonal combination test are designed to investigate the influence of the test factors, including crank length, crank rotation speed, and forward speed on the repeated-cutting rate and the miss-cutting rate. Comprehensively considering the stability and reliability of cutting, power consumption, device design, and processing difficulty, the optimal operating parameters of the cutting device are obtained as crank length 19 mm, crank rotation speed 650 r/min, and forward speed 0.5 km/h. On this basis, the fitted regression equations of the repeated-cutting rate and the miss-cutting rate are established, the miss-cutting rate and the repeated-cutting rate under the optimal parameters are 1.519% and 28.503%, and the corresponding errors with the simulation values are obtained as 11.36% and −0.45%, respectively, which verified the validity of the fitted regression equations. In the present investigation, the motion behavior of the single-blade cutting device is methodically examined for the first time, and the cutting motion rules of the cutter are illustrated. The research results aim to provide a fairly solid theoretical basis and practical reference for the optimization design of the in-soil cutting device of GLVs’ orderly harvester. Full article

This paper proposes a transition control strategy for a rotary double-inverted pendulum (RDIP) system using a sim-to-real reinforcement learning (RL) controller, built upon mathematical modeling and parameter estimation. High-resolution sensor data are used to estimate key physical parameters, ensuring model fidelity for simulation. The resulting mathematical model serves as the training environment in which the RL agent learns to perform transitions between various initial conditions and target equilibrium configurations. The training process adopts the Truncated Quantile Critics (TQC) algorithm, with a reward function specifically designed to reflect the nonlinear characteristics of the system. The learned policy is directly deployed on physical hardware without additional tuning or calibration, and the TQC-based controller successfully achieves all four equilibrium transitions. Furthermore, the controller exhibits robust recovery properties under external disturbances, demonstrating its effectiveness as a reliable sim-to-real control approach for high-dimensional nonlinear systems. Full article