Simple Mechanical Design Research Articles

Controlling a Quadcopter with Static Loads and Dynamic Wind Disturbances using a Fuzzy Inference System

Maneuverability, hover, and simple mechanical design are the advantages of quadcopters. However, because quadcopters are smaller and lighter, they are more susceptible to wind than manned aircraft. The winds that cause air accidents are divided into several categories, namely downburst, turbulent wind, wind shear, and wind vortices. Disturbances and uncertainties, such as wind gusts, can result in difficulties in executing a mission on an accurate flight path. Quadcopter resilience is an important topic for UAV. Especially if the quadcopter is in terrain that is difficult for humans to reach. Hence, the system is susceptible and experiences reduced stability. Controlling a quadcopter with a cube-shaped static load to withstand turbulent wind gusts in this research uses robust Fuzzy Inference System control and trajectory control using LQR with Command-Generator Tracking. The results achieved through fuzzy control can fortify the quadcopter against half of the overall turbulent wind gusts with an RMSE of 0.0546. In contrast with the LQR-CGT control, which still exhibits an RMSE of 0.0795.

Development of a Six-Degree-of-Freedom Analog 3D Tactile Probe Based on Non-Contact 2D Sensors.

In this paper, a six-degree-of-freedom analog tactile probe with a new, simple, and robust mechanical design is presented. Its design is based on the use of one elastomeric ring that supports the stylus carrier and allows its movement inside a cubic measuring range of ±3 mm. The position of the probe tip is determined by three low-cost, noncontact, 2D PSD (position-sensitive detector) sensors, facilitating a wider application of this probe to different measuring systems compared to commercial ones. However, several software corrections, regarding the size and orientation of the three LED light beams, must be carried out when using these 2D sensors for this application due to the lack of additional focusing or collimating lenses and the very wide measuring range. The development process, simulation results, correction models, experimental tests, and calibration of this probe are presented. The results demonstrate high repeatability along the X-, Y-, and Z-axes (2.0 µm, 2.0 µm, and 2.1 µm, respectively) and overall accuracies of 6.7 µm, 7.0 µm, and 8.0 µm, respectively, which could be minimized by more complex correction models.

Nonlinear optimal control for robotic exoskeletons with electropneumatic actuators

Nonlinear optimal control for robotic exoskeletons with electropneumatic actuators

NU-Biped-4.5: A Lightweight and Low-Prototyping-Cost Full-Size Bipedal Robot

This paper presents the design of a new lightweight, full-size bipedal robot developed in the Humanoid Robotics Laboratory at Nazarbayev University. The robot, equipped with 12 degrees of freedom (DOFs), stands at 1.1 m tall and weighs only 15 kg (excluding the battery). Through the implementation of a simple mechanical design and the utilization of off-the-shelf components, the overall prototype cost remained under USD 5000. The incorporation of high-performance in-house-developed servomotors enables the robot’s actuation system to generate up to 2400 W of mechanical power, resulting in a power-to-weight ratio of 160 W/kg. The details of the mechanical and electrical design are presented alongside the formalization of the forward kinematic model using the successive screw displacement method and the solution of the inverse kinematics. Tests conducted in both a simulation environment and on the real prototype demonstrate that the robot is capable of accurately following the reference joint trajectories to execute a quasi-static gait, achieving an average power consumption of 496 W.

Towards intelligent design assistants for planar multibody mechanisms

AbstractGeneral‐purpose mechanisms can perform a broad range of tasks but are usually rather heavy and expensive. If only particular movements need to be executed, more efficient special‐purpose mechanisms can be employed. However, they typically require an expert to design the system based on manual inspection of simulations and experimental results. This procedure is not only time‐consuming, but the outcome also depends on the expert's experience. Hence, the design process stems from subjective criteria while only a limited number of structurally different mechanisms can be considered. In contrast, a design assistant can consider a broad range of mechanisms and leverage multi‐objective optimization to retrieve optimal designs for the given task. Due to the systems being synthesized based on mathematical functions rather than individual experience, the assistant allows a more transparent development of optimal problem‐specific mechanisms compared to the conventional process. Experts can then fine‐tune and analyze the proposed designs to compose the final system. In recent years, neural networks have been utilized to directly learn the inverse mapping from a trajectory to a mechanism design. This requires some parameterization of the trajectory to be fed into the network. In this work, we evaluate various preprocessing methods for the trajectory on a simple mechanism design model problem. We assess multiple configurations such as different neural network sizes, applying input‐output normalization, and varying the number of features. Consequently, we investigate and compare the trends and robustness of the implemented methods.

Ray-Tracing Model for Generalized Geodesic-Lens Multiple-Beam Antennas

geodesic-lenses are a compelling alternative to traditional planar dielectric lens antennas, as they are low loss and can be manufactured with a simple mechanical design. However, a general approach for the design and analysis of more advanced geodesic-lens antennas has been elusive, limiting the available tools to rotationally symmetric surfaces. In this article, we present a fast and efficient implementation built on geometrical optics and scalar diffraction theory. A numerical calculation of the shortest ray path (geodesic) using an open-source library helps quantify the phase of the electric field in the lens aperture, while the amplitude is evaluated by applying ray-tube power conservation theory. The Kirchhoff-Fresnel diffraction formula is then employed to compute the far field of the lens antenna. This approach is validated by comparing the radiation patterns of a transversely compressed geodesic Luneburg lens (elliptical base instead of circular) with the ones computed using commercial full-wave simulators, demonstrating a substantial reduction in computational resources. The proposed method is then used in combination with an optimization procedure to study possible compact alternatives of the geodesic Luneburg lens with size reduction in both the transverse and vertical directions.

Very Compact Waveguide Orthomode Transducer in the K-Band for Broadband Communication Satellite Array Antennas

A very compact waveguide orthomode transducer (OMT) is described in this paper. The design is characterized with a twofold rotationally symmetric cross-section in the probing area, adapted from a side-coupling OMT design, simultaneously enabling low port-to-port coupling and high cross-polarization discrimination (XPD) over a fractional bandwidth of about 15-20%. Compared to previously reported compact waveguide OMTs, the proposed design is simpler, thus facilitating its manufacture at millimeter-wave frequencies. The concept is demonstrated with a design in the K-band for a broadband communication satellite downlink over the frequency band of 17.3-20.2 GHz. For test purposes, transitions to standard waveguide WR42 are included, and the OMT is assembled with a conical horn antenna. The measured reflection and coupling coefficients are below -19.5 dB and -22.9 dB, respectively, over the nominal bandwidth, and they are in good agreement with the simulation's results. The on-axis XPD, measured in an anechoic chamber, is better than 30 dB over the nominal bandwidth, which is also in line with simulations. The proposed waveguide OMT may be designed to fit in a lattice below one wavelength at the highest operating frequency, which is desirable for dual-polarized closely spaced array antennas in low and medium Earth orbit communication satellite systems. The simple mechanical design of the proposed OMT makes it particularly appealing for additive manufacturing techniques, as demonstrated with a variant of the design having folded single-mode waveguides, which preserves the RF properties of the original design.

A Circularly Polarized Parallel Plate Waveguide Lens-Like Multiple-Beam Linear Array Antenna for Satcom Applications

This work presents a full metal circularly-polarized lens-like antenna for Satcom applications at Ka-band. The antenna is composed of two continuous parallel plate waveguide (PPW) quasi-optical beamformers (QOBF), feeding an array of septum polarizers to generate circular polarization. The QOBFs operate over a wide band and provide a multi-beam coverage over a large field of view in the azimuthal plane, while maintaining a relatively simple mechanical design. The array of septum polarizers is based on a stepped profile to generate circular polarization with a good polarization purity in the uplink of Ka-band (27 - 31 GHz). The antenna is fully realized in aluminium. The antenna system provides 14 beams with alternating right/left handed circular polarization (RHCP/LHCP) with an axial ratio (AR) below 3 Db over an angular range of ±19° in the uplink of Ka-Band. The maximum gain in the azimuthal plane at 30 GHz is about 21 dB over the whole angular range, with a scan loss lower than 1.5 dB. The antenna efficiency is better than 78% for all beams in the operative band.

Stable Zn Anodes with Triple Gradients.

Aqueous zinc-ion batteries are highly desirable for sustainable energy storage, but the undesired Zn dendrites growth severely shortens the cycle life. Herein, a triple-gradient electrode that simultaneously integrates gradient conductivity, zincophilicity, and porosity is facilely constructed for a dendrite-free Zn anode. The simple mechanical rolling-induced triple-gradient design effectively optimizes the electric field distribution, Zn2+ ion flux, and Zn deposition paths in the Zn anode, thus synergistically achieving a bottom-up deposition behavior for Zn metals and preventing the short circuit from top dendrite growth. As a result, the electrode with triple gradients delivers a low overpotential of 35mV and operates steadily over 400h at 5mA cm-2 /2.5mAhcm-2 and 250h at 10mAcm-2 /1mAhcm-2 , far surpassing the non-gradient, single-gradient and dual-gradient counterparts. The well-tunable materials and structures with the facile fabrication method of the triple-gradient strategy will bring inspiration for high-performance energy storage devices.

Review of Cleaning Methods for Solar Cell Array

With the fossil fuels in the verge of exhaustion, the renewable sources are being seen as the prospective potentials for energy, the solar photo voltaic technology is one such source that can look up. One of the problems in installing solar energy is pollution/dust and reduces the efficiency of the photovoltaic cell and major power loss when unwanted obstructions cover the surface of the panels. The obstruction turns the shaded cell into a resistor, causing it to heat up and consume extra power. There is urgency in improving the efficiency of solar power generation, to address this issue, we have discussed about self-cleaning solar panel, and different types of mechanical cleaning technology for solar panels in this paper.A transparent electrode material such as indium tin oxide delivers an alternating current to the top surface of the panel. As it swings between being positively and negatively charged, it creates an electric field that repels charged particles/dust.A fully automated, simple mechanical design use a rotating brush made up of soft microfiber in conjunction with air blowers which will remove all dust without water and without scratching.A nano-coating with hydrophobic and self-cleaning properties for photo voltaic panels, the coating’s effect stops dust and bird faeces from sticking to PV panels, keeping them clean, maintaining their efficiency.

On the complexity of dynamic mechanism design

We introduce a simple dynamic mechanism design problem in which the designer offers two items in two consecutive stages to a single buyer. The buyer's joint distribution of valuations for the two items is known, and the buyer knows the valuation for the current item, but not for the one in the future. The designer seeks to maximize expected revenue, and the mechanism must be deterministic, truthful, and ex-post individually rational. We show that finding the optimum deterministic mechanism in this situation — arguably one of the simplest meaningful dynamic mechanism design problems imaginable — is NP-hard. We also prove several positive results, including a polynomial-time linear programming-based algorithm for the revenue optimal randomized mechanism (even for many buyers and many stages). We prove strong separations in revenue between non-adaptive, adaptive, and randomized mechanisms, even when the valuations in the two stages are independent.

A lightweight wearable biomechanical energy harvester

Human body energy harvesting has the potential to replace batteries to power wearable and mobile devices. However, the human body energy-harvester may impede human motion, be too heavy to carry, and increase the metabolic cost. In this paper, we present a lightweight device that generates electricity by harvesting energy from the negative muscle work of the human ankle and does not interfere with the natural motion of the human body. The energy harvester mounts on the leg and selectively engages to generate power in the terminal stance phase, during which the calf muscles are doing negative work. The engagement and disengagement are done by a simple but effective passive mechanism design. The modeling of the energy harvester was developed using the Lagrangian method and the energy-harvesting process was simulated to guide the device design, specifically choice between torsional stiffness, inertia, and damping terms for energy harvesting as well as human comfort. A test participant walking with the 100 g device on a treadmill at 4.8 km h−1 produced an average of 0.3 of electric power from the negative-muscle-work phase. Electromyography and torque measurement verified that the energy harvested comes from negative muscle work.

Design and analysis of an innovative flapping wing micro aerial vehicle with a figure eight wingtip trajectory

Abstract. A multi-mode flapping wing micro air vehicle (FWMAV) that uses a figure eight wingtip motion trajectory with wing flapping, rotation, and swing motion is presented in this paper. The flapping wing vehicle achieves three active degrees of freedom (DOF) wing movements only with one driving micromotor which has a good balance in the mechanism design (that is inspired by natural fliers) and total weight. Owing to these characteristics being integrated into the simple mechanism design, the aerodynamic force is improved. The aerodynamic performance of the thrust force is improved by 64.3 % compared to one that could only flap up and down with one active DOF under the condition of routine flapping frequency.

Ranking reversals in asymmetric auctions

This paper compares the first-price auction and the second-price auction with several asymmetric bidders who are either weak or strong. The ranking of these auctions in terms of profit may flip as the exogenous reserve price or the number of weak or strong bidders change. Similarly, with endogenous reserve prices the ranking may depend on the seller’s own-use valuation. In other words, the ranking may be fragile to changes along these dimensions. Existing models rule out such ranking reversals by imposing substantial structure on type distributions. The current paper relies on simple mechanism design arguments that require less structure.

A novel three-legged 6-DOF parallel robot with simple kinematics

This paper presents a novel three-legged six degrees of freedom (6-DOF) parallel robot with simple kinematics. The main idea behind this novel architecture is that each of the three identical legs is controlled by two prismatic actuators with parallel directions. As a result, it is possible to control simultaneously or separately the position and the orientation of a leg. The reduced number of legs leads to a simple mechanical design with reduced risk for mechanical interferences.

Attenuation of low-frequency sound in U-shaped duct with membrane coupled acoustic resonator: Modeling and analysis

This study proposes a new solution to control low-frequency noise in acoustic duct. The control device is in the shape of a Helmholtz resonator combined with a tensioned membrane in the air cavity, referred to as a membrane resonator. The membrane resonator is connected to the main waveguide through two necks. A theoretical model is developed to evaluate its acoustic performance when attached to a U-shaped duct as the host structure. Numerical simulation shows that the proposed resonator generates effective transmission loss in the very low-frequency region, as a result of the vibro-acoustic coupling between the integrated membrane and the two-end Helmholtz resonator. Since the attenuation band is deep sub-wavelength, a lumped-mass model is developed to capture the main physics involved in the acoustical-mechanical coupling. With the developed models, the tuning range of the proposed system is further investigated. Several tuning mechanisms are demonstrated by changing the membrane tension, thickness, material type and combining multiple resonators. The transmission loss has fairly large variation range and the desired frequency band is fully controllable. The proposed resonator has simple geometry and mechanical design, whilst the deep sub-wavelength characteristics and the offered tunability are promising. It has the potential to be used solely or as the basic building block in a wide range of noise control applications.

Radial Force Minimization Control for Fault-Tolerant Switched Reluctance Machines With Distributed Inverters

Switched reluctance machines (SRMs) are known for their simple and robust mechanical design, low magnetic pole, and phase coupling as well as low short-circuit current and open-circuit voltage during a fault condition. These advantages make the SRM a suitable candidate for applications, which requires high-reliability and fault-tolerant operation. This article addresses the challenge of minimizing the unbalanced magnetic pull (UMP) caused during a single-pole failure, which is the most common electrical fault found in SRMs. In fault-tolerant SRMs, usually, the entire faulty phase is turned off to continue operation. To minimize the loss of torque production during a fault, a distributed inverter (one inverter module per coil) is introduced enabling the SRM to continue operation with all remaining healthy poles. Furthermore, a fault-tolerant control strategy utilizing the advantages of the distributed inverter, namely, radial force minimization control (RFMC), is proposed. This control allows a considerable reduction in the UMP while maintaining constant torque control during faulty operation. A four-phase 1-kW 16/12 SRM with a distributed inverter is used to present the theoretical approach and simulation results of the proposed control algorithm. Furthermore, experimental measurement results for the RFMC are shown to validate the effectiveness of the introduced algorithm.

Piezo-electric transducer actuated mirror with a servo bandwidth beyond 500 kHz.

We demonstrate a novel system that uses a piezoelectric transducer (PZT)-actuated mirror for laser stabilization. A combination of a simple mechanical design and electronic circuits is used to realize an ultra-flat frequency response, which enables an effective feedback bandwidth of 500 kHz. The PZT also performed well when used in a mode-locked laser with a GHz repetition rate, to which it is difficult to apply an electro-optic modulator (EOM).

A Simple Mechanical Model for Synthetic Catch Bonds

Summary Catch bonds are protein-ligand bonds that become more difficult to break as the applied force increases, a counterintuitive phenomenon that has not yet been reproduced in synthetic systems. Here, we have demonstrated that a simple mechanical design based on a tweezer-like mechanism can exhibit catch bond characteristics under thermal excitations. The tweezer has a force-sensitive switch that controls the transition of the system to a high-ligand-affinity state with additional ligand-tweezer interactions. Applying kinetic theory to a two-mass-two-spring idealized model of the tweezer, we show that by tuning the shape of the switch and the ligand-tweezer interaction energy landscapes, we can achieve greater lifetimes at larger force levels. We validate our theory with molecular dynamics simulations and produce a characteristic lifetime curve reminiscent of catch bonds. Our analysis reveals minimal design guidelines for reproducing the catch bond phenomenon in synthetic systems such as molecular switches/foldamers, DNA linkers, and nanoparticle networks.

Bio-inspired anti-vibration with nonlinear inertia coupling

Abstract This paper presents a unique human body inspired passive vibration isolation system with a special coupled nonlinear inertia design. This human body inspired anti-vibration structure with nonlinear inertia consists of a compact X-shaped structure with a horizontally-installed spring system to simulate the functions of legs and muscles, and a compact rotational unit to mimic the arms swinging (or upper body movement) and/or muscle extension-flexion motion during human walking. It is particularly focused on the beneficial nonlinear effect incurred by the rotational unit, including a nonlinear equivalent mass and a very special nonlinear inertia incurred conservative force. It is shown that, the nonlinear properties (in equivalent stiffness, damping and mass simultaneously) can obviously improve the vibration isolation at low frequencies and/or in a broadband frequency range, and increase the stability of the mass center of the overall isolation system during vibration, irrespective of the loading and excitation conditions. The muscle function and swinging arms of human body are for the first time employed with an innovative and simple mechanical design for vibration control and successfully validated by experimental prototypes for their excellent beneficial nonlinear features. This paper presents a unique simple passive and adjustable anti-vibration solution of great potential in extensive engineering applications.