Design of multimodal transformable wheels for amphibious robotic vehicles

<div class="section abstract"><div class="htmlview paragraph">In response to the complex shore slope road conditions and the switching of water–land environments during the amphibious vehicle’s landing process, a landing drive force control strategy for amphibious vehicles is proposed. First, based on the shore slope gradient, buoyancy effect, and amphibious vehicle acceleration, the drive force of the front and rear wheels of the amphibious vehicle is pre-allocated. Then, referring to the road parameters of common road types, the road adhesion coefficient and optimal slip ratio of the current road surface where the amphibious vehicle is located are identified based on the principle of fuzzy control. Subsequently, with the slip ratio difference as the control target, the drive motor is controlled based on the sliding mode control algorithm to achieve tracking of the optimal slip ratio. A joint simulation is carried out using CarSim and Simulink, and the results are compared with those without control. The simulation results show that the drive force control strategy proposed in this paper can reduce the water-to-land time by 9.1 s and quickly reduce the wheel slip ratio to below 0.2, controlling it near the optimal slip ratio, thereby improving the vehicle’s power and stability.</div></div>

The water resistance of wheeled amphibious vehicles directly affects their water performance, and indicators such as navigation trim angle and center of gravity heave value directly affect their water stability performance. The initial trim angle of amphibious vehicles has a significant impact on these indicators, which is very important in wheeled amphibious vehicle design. This article studies the influence of initial trim angle on the water resistance, navigation trim angle, and heave value at the center of gravity of a certain wheeled amphibious vehicle through model test, providing relevant basis for designing the initial trim angle of this wheeled amphibious vehicle.

Pump-jets have a relatively high propulsion efficiency at medium speed and in heavy-load conditions for wheeled amphibious vehicles. However, the geometry of amphibious vehicles is very special due to the installation requirements of the pump-jet, which results in an obvious resistance on the wheels. In order to reduce the resistance of the amphibious vehicle, the resistance characteristics of the wheels are studied. Regarding a pump-jet-propelled wheeled amphibious vehicle, its wheel resistance characteristics in a wide speed range are firstly analyzed based on experiments and numerical simulations. By comparing the resistance of the amphibious vehicle with and without wheels, it is found that the hydrodynamic effect of wheels can increase the total resistance of the amphibious vehicle by 14~28%. Then, the wheel hydrodynamic effect is divided into local effect and global effect. By analyzing the changes in resistance, pressure distribution and streamline, the influence and hydro-mechanism of each effect are explored in detail. It is found that the longitudinal convex and concave structures formed by the wheels and wheel wells have a large negative effect on the total resistance. According to the hydro-mechanism, two resistance improvement approaches are proposed, which includes increasing wheel retraction and installing flat plates on the wheel well bottom. Finally, the ultimate resistance improvement model can reduce resistance by no less than 10% and power by on less than 8% in design speed.

Amphibious vehicles play an important role in logistics support and material transportation. However, the problem of poor traction and passability of amphibious vehicles in the tidal flat area still needs to be solved urgently. In order to solve the problems, a wheel-track composite amphibious vehicle (W-TCAV) driving system is proposed, and the high mobility of wheeled vehicles and the high passability of tracked vehicles are integrated; According to the configuration of the W-TCAV, the model of terramechanics and driving kinematics are established; Based on the control program of Matlab/Simulink, it is verified that the W-TCAV has obvious advantages compared with wheeled vehicles in terms of traction and passability; Based on the driving characteristics of W-TCAV, the influence of power matching on the traction passability is studied. The simulation results show that the traction performance of the W-TCAV can be effectively improved in the tidal flat area, and the traction performance can be significantly ameliorated by maintaining the consistency of wheel-track power matching.

Typically, a twisting morphing wing of flying or swimming robots has one spanwise shaft and many ribs, the ribs can swing in their individual planes perpendicular to the shaft or the spanwise direction of the wing, showing different swing angles and different speed ratios with respect to the rotation of the shaft, thus the wing can form various degrees of spanwise twisting as the shaft rotates. While feasible solutions and mechanical implementations via gear transmission with tight geometric constraints are largely unexplored. This article considers the tight geometric constraints for such robotic twisting wing, and provides and particularly expands the analytical feasible solutions for the constraints, as well as provides mechanical implementations for active twisting of the wing that is driven by only one motor installed at the wing base, which implementations are compact with low inertia, low control complexity, and also high robustness that tolerates the deformations (e.g., bending due to load) of the shaft. The results serve as a design guidance and can be used for morphing wings of flying or swimming robots, particularly for accurately active spanwise twisting and large load transmissions to the movable parts.

The Modular Multilevel Converter (MMC) has been recently accepted as an advantageous choice for high-voltage applications. However, for extending this topology to higher voltages, the number of its submodules should be increased. On the other hand, using high-frequency carrier-based modulation schemes is very popular for voltage-source converters; since they provide improved output quality, and don't involve complex calculations. When this strategy is employed for MMCs, the number of carriers would increase for more submodules, and the control complexity and required memory become more as result. Moreover, synchronizing several carriers is another issue. In this paper, a novel PSC-PWM scheme with low control complexity is proposed. The number of carriers employed in the designed scheme is always two, and independent of the submodule numbers. Despite this fact, the benefits of the conventional PSC-PWM, like the excellent harmonic content for different operating points, are completely remained. The performance of the proposed method is validated through conducting simulations in the MATLAB/Simulink environment.

SUMMARYIn this paper, we focus on the configuration design of a reconfigurable robot that merges the functions of wheels, tracks, and legs together. A deformable rim is utilized to make the robot wheel reconfigurable to change its locomotion mode. Three rules of configuration design to achieve reconfiguration between different modes are proposed: (1) in wheel mode, the track wheel set should be hidden inside the wheel rim; (2) in track/leg mode, the folded wheel rim should be hidden inside the caterpillar loop; (3) the circumference of the wheel rim in wheel mode should be equal to the length of the track ring in track mode. According to these rules, the configuration of the deformable rim, track wheel set, and telescopic spoke are analyzed and designed. A prototype of the reconfigurable wheel is fabricated by three-dimensional printing, and its functions of locomotion in different modes, the switch between different modes, and its load-bearing ability are tested, verifying the effectiveness of the configuration design. Furthermore, a prototype of the reconfigurable robot is manufactured by computerized numerical control (CNC) machining to verify the structural design of the reconfigurable wheel. Compared to traditional hybrid robots with separate wheels, tracks, and legs, this reconfigurable design lends the multimodal robot both excellent terrain adaptability and a compact structure; thus, it can be widely used as a universal mobile platform in search and rescue missions and explosive object disposal missions.

Amphibious vehicle has blunt bow and multi appendage structure, and its flow field characteristics are very complicated during maneuvering. In this paper, a simplified model of amphibious vehicle with propulsion device is established, and the thrust volume force model is introduced to consider the pumping and water jet propulsion of the water effects jet propulsion device. The technique of overlapping grid is used to deal with the six-degree-of-freedom large-scale hull motion problem, and study the turning motion of amphibious vehicle under different rudder angles. The results of numerical simulation show that the amphibious vehicle will enter a stable turning state when turning on the water surface, but the heel angle is large, the draft depth and the speed drop are significant. The state of water baffle has a significant influence on vehicle trim and roll motion. Larger vehicle pitching motion amplitude will increase the risk of overturning.

Due to the increasing penetration level of wind power in power system, wind turbines can provide less frequency support than conventional generators due to their small rotor mass. This makes the power system with low inertia and hence cause frequency problem. This paper has proposed an integrated control strategy for participate in primary frequency control by doubly fed induction generation (DFIG). According to the reserve capacity required for primary frequency control, a de-loading control method is also proposed in this paper to resolve the issue of inertia control and primary frequency control. Based on the analysis method of the frequency control characteristics of DFIGs, the frequency control strategy can adjust the static frequency difference coefficient and it is proposed by improved variable pitch control method. Furthermore, the virtual inertia control and the primary frequency control can be integrated a control strategy of DFIGs. The simulation results show that the DFIGs can provide an effective inertia support to reduce the system frequency changing rate in the inertia process and improve the static frequency stability of power system by the static frequency characteristics.

The automotive industry is undergoing a transformative shift towards electric vehicles (EVs), driven by environmental concerns and technological advancements. One critical aspect of EV design is the development of lightweight yet robust components, including 3D vehicle wheels. This research explores the implementation of generative models in Computer-Aided Design (CAD) systems to optimize the design of 3D vehicle wheels for electric vehicles. Through the use of generative design and additive manufacturing, we aim to create vehicle wheels that are energy-efficient, aesthetically pleasing, and structurally sound. Electric vehicles are gaining popularity due to their environmental benefits and reduced operating costs, making lightweight and strong wheels an important design goal. This research proposes a novel approach for designing lightweight and strong 3D vehicle wheels for EVs using generative models. The proposed approach involves the following steps: collect and prepare data, choose a generative model architecture, train the generative model, and generate new wheel designs. The approach methods show potential to revolutionize the design and manufacturing of lightweight and strong 3D-printed wheels for electric vehicles. In conclusion, generative models can be used to design and optimize wheel designs, making it possible to create safer, more efficient, and more cost-effective wheels.

Focus on Magnetics

This paper proposes an efficient and simple architecture for 9/7 Discrete Wavelet Transform based on Distributed Arithmetic. To derive new proposed architecture, we consider the periodicity and symmetry of DWT to optimize the performance and reduce the computational redundancy. The inner product of coefficient matrix of DWT is distributed over the input by careful analysis of input, output and coefficient word lengths. In the coefficient matrix, linear maps are used to assign the necessary computation to processing elements in space domain. Moreover, the proposed architecture has regular data flow, and low control complexity. The result is a low hardware complexity DWT processor for 9/7 transform, which allows two times faster clock than the direct implementation. This design is very suitable for image compression systems, e.g., JPEG2000 and MPEG4.

Architectures for optical TDM switching with low control complexity, which would be suitable for implementation with lithium niobate switches and fibre delay lines, are discussed. The networks are mathematically equivalent to strictsense nonblocking Cantor networks, and use the same control algorithm. The penalty paid for low control complexity is a large number of components. All such networks use ‘feed-forward’ delay lines which provide superior crosstalk performance and more uniform attenuation than existing designs. Architectures, both with and without frame integrity, are considered; performance is characterised in terms of attenuation and crosstalk.

Due to the large amount of data transfers it involves, the motion estimation (ME) engine is one of the most power-consuming components of any predictive video codec. As a consequence, power-optimized video coding primarily relies on a carefully designed motion estimator. This paper first presents a block ME algorithm that meets high-quality inter-frame prediction and low computational complexity requirements. It relies on a set of rules common to all recent fast and adaptive ME algorithms, but is designed in order to allow for easy and prolific data reuse. The adjacent order of the candidate positions during the search increases the locality and maintains a near-regular data flow, which results in a decrease of the data transfers and a low control complexity. Together with, the computational complexity reduction, it enables cost-efficient very large scale integration realizations. A pipelined parallel architecture is then proposed and discussed. It is generic in the sense that it is suited both to the full-pel and half-pel ME. I It is efficient, because it allows for close to 100% hardware utilization and a sharp decrease of the peak memory bandwidth. It is suited to low-power implementation, as it enables larger data reuse factors for the most probable stages of the adaptive algorithm, which reduces the average memory bandwidth and power consumption.

Commercial-off-the-shelf (COTS) devices enabled visible light communication (VLC) for Internet of things (IoT) applications has attracted extensive attentions from both academic and industrial communities, thanks to the pervasive deployments of light emitting diode (LED) lighting infrastructure. However, due to the limitation of frequency response and non-linearity of the commercial illuminating LED light consisting of multiple LED chips, the achievable data rate is far less than that provided by the experimental VLC system with a single LED with specialized devices, e.g., lens. To this end, we propose a power-of-2 arrangement scheme for LED chips to generate spatial summing modulation with low control complexity, and demonstrate its availability in an orthogonal frequency division multiplexing (OFDM) VLC system purely built upon COTS devices. It significantly differs from a conventional OFDM VLC system relying on digital-to-analog converter (DAC) and analog signal chain, which is complex and confined by LED's non-linearity, thanks to we design a novel digital-to-light converter (DLC) which can output 256 light intensities linearly and be directly controlled by the discrete digital signals generated by the OFDM modulator. An experimental demonstration with employing the QAM-OFDM modulation scheme successfully confirms the effectiveness of the proposed spatial summing VLC system, which can achieve low BERs of below the forward error correct (FEC) threshold of 3.8×10-3 for both QAM8 and QAM16 running transmission frequency of 300 kHz under a communication distance of 0.8 m. It demonstrates the promising potential for delivering a data rate at hundred kbps level with this novel spatial summing based OFDM VLC system, which is sufficient for many IoT applications.