Compliant Suspension Research Articles

Design and Analysis of a Lunar Crewed Vehicle With a Novel Versatile Compliant Suspension Mechanism

Abstract A lunar crewed vehicle (LCV) with improved maneuverability, mobility, and ride comfort is required for astronauts to conduct long-range scientific investigations and resource utilization on the Moon’s surface. This paper concentrates on designing a novel multi-functional compliant suspension for LCV to improve the above-mentioned performance. First, based on the requirement of high-speed traversing on the rough Lunar terrain, the required type of suspension motion is identified and the demanded suspension mechanism is obtained through structural evolution. Then, the kinematic analysis of the proposed suspension mechanism is conducted, and the steering kinematic model of the whole vehicle is established. A compliance analysis is completed, taking into account the actual design characteristics of the suspension mechanism. A multi-degrees-of-freedom dynamics model of the vehicle is developed, considering both wheel–ground separation and the deformation of wheels and soil. Simulations are conducted to verify full vehicle performance with the proposed suspension, and the results reveal that the design features better mobility and comfort in rough terrain with minimum turning radius, peak longitudinal acceleration, and root mean square reduced by 9.5%, 45.1%, and 21.4%, respectively.

Bistable Rotational SOI Actuator With a Planar Tripod Compliant Suspension

Bistable Rotational SOI Actuator With a Planar Tripod Compliant Suspension

Modular speaker design enabled by multi-material additive manufacturing

One of the most promising features of additive manufacturing is ability to reduce part count and assembly by printing complex shapes. This feature is further highlighted by utilizing multi-material printing in which stiff and compliant materials can be deposited by the same system. Air-acoustic speakers are traditionally comprised of several assembled components with different material properties including a stiff enclosure, stiff diaphragm, and compliant suspension. In this presentation, we will describe a modular acoustic speaker design. The design consists of fully printed structural components (which are threaded together, and assembled with a voice coil and magnet). The basic design as well as printing process will be described and acoustic measurements reported. A range of printed designs, which can be interchanged among each-other will be presented, and future design ideas which take advantage of the printing process explored.

A novel compliant mechanism based system to calibrate spring constant of AFM cantilevers

Calibrating spring constant of atomic force microscope (AFM) cantilevers is necessary for the measurement of micro/nano newton forces, which are commonly-used in the characterization of micro/nano functional surfaces and materials, cell manipulation, and many more applications. This paper presents a novel compliant mechanism based system to calibrate the spring constant of AFM cantilevers. The calibration system is mainly composed of a compliant suspension mechanism and an electromagnetic force actuator, where two kinds of compliant structures of “L” shape flexures and “Archimedes” planar flexures are assembled in parallel to achieve compact devices, respectively. The characteristics of the suspension mechanism are investigated by analytical model and finite element analysis (FEA). Furthermore, a prototype of the calibration system is established and experimental tests are carried out to verify the performance. An electromagnetic force actuator is employed to provide calibration force. Meanwhile, a capacitance sensor is utilized to monitor the displacement of the suspension mechanism. The calibration results of AFM cantilevers reveal that the compliant mechanism based calibration system has a good performance and it can calibrate the spring constant of AFM cantilevers accurately and effectively.

Design of Track-Type Climbing Robots Using Dry Adhesives and Compliant Suspension for Scalable Payloads

AbstractClimbing robots offer advanced motion capabilities to perform inspection, manufacturing, or rescue tasks. Climbing requires the robot to generate adhering forces with the climbing surface. Dry adhesives present a category of adhesion that could be advantageous for climbing a variety of surfaces. Current literature shows climbing robots using dry adhesives typically exhibit minimal payloads and are considered useful for tasks involving lightweight sensors, such as surveillance. However, dry adhesives routinely demonstrate adhering pressures in the range of 20–50 kPa, suggesting that a small robot (3 × 30 cm footprint, for example) could theoretically have a significant payload (in the order of 18–45 kg). Existing designs demonstrate small payloads primarily because they fail to distribute the adhesion forces over the entire adhering region available to these robots. Further, existing design methods do not demonstrate scalability of payload-to-vehicle size but, in fact, indicate such robots are not scalable (Gorb et al., 2007, “Insects Did It First: A Micropatterned Adhesive Tape for Robotic Applications,” Bioinspir. Biomim., 2(4), pp. 117–125.). This paper presents a design procedure for track-type climbing robots that use dry adhesives to generate tractive forces and a passive suspension that distributes the climbing loads over the track in a preferred manner. This procedure simultaneously considers the behavior of both the adhesive material at the track-surface interface and the distribution of the adhesive forces over the full contact surface. The paper will demonstrate that dry-adhesive-based climbing robots can be designed to achieve high payloads and are scalable, thus enabling them to be used in applications previously thought to be impossible with dry adhesives.

Effect of compliant linkages on suspension under load

Abstract. A numerical investigation is performed into the effects of rigid and compliant suspension linkages, respectively, on: the kinematics and handling performance of a lightweight electric vehicle (EV). CAE models of the front and rear suspension systems are first established based on the measured parameters of the target vehicle. The validity of the CAE models is confirmed by comparing the results obtained for the camber angle and kingpin inclination angle with those obtained mathematically using the vector loop method. CAE models are then performed using half-vehicle and whole-vehicle models. Quarter-vehicle simulations are then performed to compare the solutions obtained from the compliance and rigid-body models for the forces acting on the hardpoints of the two suspension systems under pothole impact conditions. Finally, whole-vehicle simulations are conducted using both the rigid-body model and the compliance model to evaluate the handling performance of the EV in impulse steering tests conducted at vehicle speeds of 40, 60 and 80 km h−1, respectively. In general, the results show that the choice of a rigid-body model or a compliance model has a significant effect on the forces computed at some of the hardpoints in the front and rear suspension systems. Furthermore, the rigid-body model predicts a better vehicle body stability following high-speed turns than the compliance model.

Development and Experimental Validation of Auxiliary Rolling Bearing Models for Active Magnetic Bearings (AMBs) Applications

Nowadays, the search for increasing performances in turbomachinery applications has led to a growing utilization of active magnetic bearings (AMBs), which can bring a series of advantages thanks to their features: AMBs allow the machine components to reach higher peripheral speeds; in fact there are no wear and lubrication problems as the contact between bearing surfaces is absent. Furthermore, AMBs characteristic parameters can be controlled via software, optimizing machine dynamics performances. However, active magnetic bearings present some peculiarities, as they have lower load capacity than the most commonly used rolling and hydrodynamic bearings, and they need an energy source; for these reasons, in case of AMBs overload or breakdown, an auxiliary bearing system is required to support the rotor during such landing events. During the turbomachine design process, it is fundamental to appropriately choose the auxiliary bearing type and characteristics, because such components have to resist to the rotor impact; so, a supporting design tool based on accurate and efficient models of auxiliary bearings is very useful for the design integration of the Active Magnetic Bearing System into the machine. This paper presents an innovative model to accurately describe the mechanical behavior of a complete rotor-dynamic system composed of a rotor equipped with two auxiliary rolling bearings. The model, developed and experimentally validated in collaboration with Baker Hughes a GE company (providing the test case and the experimental data), is able to reproduce the key physical phenomena experimentally observed; in particular, the most critical phenomenon noted during repeated experimental combined landing tests is the rotor forward whirl, which occurs in case of high friction conditions and greatly influences the whole system behavior. In order to carefully study some special phenomena like rotor coast down on landing bearings (which requires long period of time to evolve and involves many bodies and degrees of freedom) or other particular events like impacts (which occur in a short period of time), a compromise between accuracy of the results and numerical efficiency has been pursued. Some of the elements of the proposed model have been previously introduced in literature; however the present work proposes some new features of interest. For example, the lateral and the axial models have been properly coupled in order to correctly reproduce the effects observed during the experimental tests and a very important system element, the landing bearing compliant suspension, has been properly modelled to more accurately describe its elastic and damping effects on the system. Furthermore, the model is also useful to characterize the frequencies related to the rotor forward whirl motion.

Design and Implementation of a Bistable Force/Acceleration Sensing Device Considering Fabrication Tolerances

We report on a design methodology, fabrication, and characterization of a bistable actuator operated by a parallel-plate electrostatic transducer. The operational principle of the device, which can serve as a bifurcation-based contact-free force/acceleration sensor, is based on a pull-in voltage monitoring. Bistability appears due to the interplay between the hardening nonlinearity of straightened curved beams used as the compliant suspensions and softening nonlinearity of the electrostatic force directed along the beams. Careful mapping of the parameters at the design stage resulted in reduced device sensitivity to fabrication tolerances and allowed to ensure bistability, necessary for the functionality of the sensor. The devices were fabricated from silicon on insulator substrates using deep reactive ion etching and bistability was demonstrated experimentally. Acceleration was emulated using electrostatic force and sensitivity of 0.173 V/g was registered in experiments. Good agreement between the experimental results and the model predictions was observed. [2018-0031]

Reciprocating Geared Mechanism with Compliant Suspension

We present a novel cycloidal geared mechanism with a continuous rotational input featuring a reciprocating translational output. A statically balanced compliant mechanism suspends an annulus driven by a cycloidal rotor. The freedom and constraint topology design method is used to synthesize the compliant suspension. A fixed transmission ratio of 15 results from the ratio between the cycloidal rotor and the annulus. The static balancing conditions of the suspension are developed analytically, and validated using finite-element modeling and experimental results. Moreover, the estimation of the frictional loss as a function of the stiffness of the compliant members is derived using a force analysis of the system and verified using experimental data. A case study on a mechanical watch yields dimensions for the prototype, which is fabricated in silicon using deep reactive ion etching. Experiments show that energy loss as a function of the stiffness of compliant members is marginal and independent of the position of the compliant suspension. [2016-0260]

Non-inertial low frequency vector sensor with torsional suspension

Conventional low frequency (from 10 Hz) velocity vector sensors utilize inertial approach using neutrally buoyant body with inertial sensor (accelerometer or moving coil geophone) inside. In order to achieve high sensitivity at the low frequencies these sensors must have relatively high inertia (mass). High mass leads to increased size (such as soccer ball) of the sensor in order to satisfy the condition of neutral buoyancy. The developed alternative non-inertial sensor utilizes torsional frictionless and extremely compliant suspension enabling very light and small, yet sensitive with low resonance sensor.

Axial Suspension Compliance and Compression for Enhancing Performance of a Nonlinear Vibration Energy Harvesting Beam System

Developing energy harvesting platforms that are strongly sensitive to the low and diffused frequency spectra of common environmental vibration sources is a research objective receiving great recent attention. It has been found that utilizing designs and incorporating structural influences that induce small values of linear stiffness may considerably enhance the power generation capabilities of energy harvesting systems. This research examines these two factors in new light toward the development of a biologically-inspired energy harvesting beam platform that exploits axial compressive effects and compliant suspensions. Through theory and experiments, it is found that the strategic exploitation of such characteristics promotes dramatic improvements in the average power that may be generated for the same excitation conditions. Examining the origin of these performance enhancements, it is seen that large compliance in the compressed axial suspensions facilitates a favorable redistribution of dynamic energy, which thereby enables greater bending of the harvester beam and increased electromechanical transduction.

An adaptive pneumatic suspension system for improving ride comfort and handling

The paper describes an adaptive pneumatic suspension system that can improve both comfort and handling. Each air spring in the vehicle is connected to an auxiliary tank via two connecting pipes of different sizes. Choosing the connecting pipe with larger diameter and shorter length renders a compliant suspension which improves comfort. Conversely, choosing the connecting pipe with smaller diameter and longer length makes the suspension stiffer which favors handling. Toggling between configurations is fast, efficient, and easily done by simply opening or closing the corresponding electrovalves. The proposed adaptive system requires a GPS receiver and access to two pieces of information regarding the road at every location: the International Roughness Index and the curve radius (if not infinite). This information is used to predict road-induced vibrations and evaluate comfort with the ISO 2631 standard, as well as forecast roll angles and settling times for handling assessment. These predictions are used to select the most appropriate configuration.

A microneedle array able to inject tens of thousands of cells simultaneously

This paper presents a biological microelectromechanical system for injecting foreign particles into thousands of cells simultaneously. The system inserts an array of microneedles into a monolayer of cells, and the foreign particles enter the cells by diffusion. The needle array is fabricated using a series of deep reactive ion etches and produces about 4 million needles that average 1 μm in diameter and 8 μm in length with 10 μm spacing. The insertion of the needles is controlled through a compliant suspension. The compliant suspension was designed to provide for needle motion into the cells while restraining rotations or transverse motions that could result in tearing of the cell membranes. Testing was performed using propidium iodide, a membrane impermeable dye, injected into HeLa cells. Average cell survivability was found to be 97.7%, and up to 97.9% of the surviving cells received the propidium iodide.

Design and fabrication of a high-aspect-ratio parylene-based comb-drive actuator for large displacements at a low driving force

This paper presents a comb-drive actuator integrated with parylene-based flexible beams for large displacements at a low driving force. Single-crystal silicon and polysilicon are the traditional materials used for comb-drive actuators in the microeletromechanical systems industry. However, the larger Young's modulus limits the displacement at a low applied voltage. This study uses the parylene beams with the characteristic of a low modulus of the elastic comb-drive actuator as a compliant suspension to create a larger displacement (>50 µm) with smaller driving forces than that of silicon. High-aspect-ratio parylene beams can be fabricated through the deposition and removal of parylene in multiple stages on a silicon micro-trench. The proposed process uses a silicon-on-insulator wafer as the substrate to fabricate suspended silicon and parylene beams as rigid and compliant structures, respectively. The test devices of parylene- and silicon-based comb-drive actuators were fabricated with 100 pairs of comb fingers with gaps of 5 µm, and compliant beams of 15 µm in width, 2000 µm in span and 50 µm in thickness. When a driving voltage of 40 V dc was applied, the parylene-based comb-drive actuator generated a displacement of up to 55 µm, whereas the silicon-based comb-drive actuator generated a displacement of 2 µm. The parylene-based comb-drive actuator can generate about 27 times of displacement than that of silicon. This design is suitable for application in devices with large in-plane displacement and low switching speed.

Scalable GMP compliant suspension culture system for human ES cells

Suspension bioreactors are an attractive alternative to static culture of human embryonic stem cells (hESCs) for the generation of clinically relevant cell numbers in a controlled system. In this study, we have developed a scalable suspension culture system using serum-free defined media with spinner flasks for hESC expansion as cell aggregates. With optimized cell seeding density and splitting interval, we demonstrate prolonged passaging and expansion of several hESC lines with overall expansion, yield, viability and maintenance of pluripotency equivalent to adherent culture. Human ESCs maintained in suspension as aggregates can be passaged at least 20 times to achieve over 1×1013 fold calculated expansion with high undifferentiation rate and normal karyotype. Furthermore, the aggregates are able to differentiate to cardiomyocytes in a directed fashion. Finally, we show that the cells can be cryopreserved in serum-free medium and thawed into adherent or suspension cultures to continue passaging and expansion. We have successfully used this method under cGMP or cGMP-equivalent conditions to generate cell banks of several hESC lines. Taken together, our suspension culture system provides a powerful approach for scale-up expansion of hESCs under defined and serum-free conditions for clinical and research applications.

Design considerations of a large-displacement multistable micro actuator with serially connected bistable elements

In this work we report on a finite element modeling and design methodology, fabrication and characterization of a large-displacement low voltage multistable micro actuator with an integrated electrostatic comb drive transducer. The compliant suspension of the device incorporates multiple serially connected bistable arch-shaped beams and exhibits controllable sequential snap-through buckling under an increasing actuation force. The device can be considered therefore as an example of a compliant multistep structure. The device is also distinguished by its ability to remain in several different stable configurations at the same actuation voltage while the force–displacement characteristic of the suspension can be tailored by changing the geometry parameters of the flexures. A model built using the shallow arch approximation along with a nonlinear finite element analysis were used in order to study the influence of the suspension architecture on the stability limits of the structure and for evaluation of design parameters of the actuator. Bistable and multistable devices were fabricated by a Deep Reactive Ion Etching (DRIE) based process using silicon-on-insulator (SOI) wafers. Experimental results, which are consistent with the model predictions, demonstrate that the compliant multistep devices exhibit improved lateral stability and consequently larger stable displacements compared to the conventional comb drive actuators. Stable displacements up to 80 μm at a voltage of 30 V were registered in the experiments while three snap-through and snap-back events took place during loading and unloading, respectively. Our computational and experimental results show that the suggested device has clear functional advantages and can be efficiently used in applications including switches, threshold inertial sensors, variable optical attenuators as well as in micro-and nanomechanical logical elements.

Design, operation, and motion characteristics of a precise piezoelectric linear motor

Abstract This paper presents the design, operation, and motion characteristics of a precise piezoelectric motor for linear translation. The motor is compact, thermally stable, ultra-high vacuum compatible, and suitable for applications requiring fine resolution over millimeter-long travel ranges. Inside the motor, a translating alumina prism is symmetrically constrained within a stationary structure by a compliant suspension that preloads six shear-mode piezoelectric actuators against flat surfaces on the prism. A single step is achieved by sequentially sliding each piezoelectric actuator backward along the prism’s surfaces and then simultaneously moving all actuators forward. Many steps are repeated at 60 Hz for longer translations. Experiments indicate that: the step size is adjustable between 5 nm and 225 nm, the motor can reach speeds of 13.5 μ m/s, the step size is highly uniform with a standard deviation of about 1.2 nm, error motion in the direction orthogonal to the translation is about 800 nm peak-to-valley, and the thermal stability is better than 40 nm/ ° C.

Scaling Hard Vertical Surfaces with Compliant Microspine Arrays

A new approach for climbing hard vertical surfaces has been developed that allows a robot to scale concrete, stucco, brick and masonry walls without using suction or adhesives.The approach is inspired by the mechanisms observed in some climbing insects and spiders and involves arrays of microspines that catch on surface asperities. The arrays are located on the toes of the robot and consist of a tuned, multi-link compliant suspension. The fundamental issues of spine allometric scaling versus surface roughness are discussed and the interaction between spines and surfaces is modeled. The toe suspension properties needed to maximize the probability that each spine will find a useable surface irregularity and to distribute climbing loads among many spines are detailed. The principles are demonstrated with a new climbing robot, SpinybotII, that can scale a wide range of flat exterior walls, carry a payload equal to its own weight, and cling without consuming power. The paper also reports how toe parameters scale with robot mass and how spines have also been used successfully on the larger RiSE robot.

Bending wave loudspeaker

A loudspeaker comprising a bending-wave panel, an enclosure in which the bending-wave panel is mounted to enclose one face of the panel, a compliant suspension between the panel and the enclosure by which the panel is supported in the enclosure, a vibration exciter attached to the panel to apply bending-wave energy thereto, and an acoustic absorber in the enclosure to reduce standing waves in the enclosure, characterised in that the compliant suspension and the acoustic absorber are integral.

Criteria for handling measurement

Both handling and ride comfort play an important role in the performance of a vehicle, usually resulting in a compromised suspension. To improve this situation, a two-stage, semi-active hydro-pneumatic spring–damper system has been developed. The suspension system enables either good ride comfort for a compliant suspension or good handling when changed to a hard setting. The question that arises is, what measures can be applied to determine when a switchover between the two settings should occur. The frequency weighted mean square value of the vertical acceleration is a well-known criterion for ride comfort. For handling, several criteria have been put forward, which are to a more or lesser extent dependent on driver input. This paper considers the metrics that have been used for measuring handling and pays special attention to roll angle as a valid criterion. Results of tests performed on three different vehicles are presented. The results indicate that roll angle, lateral acceleration and yaw rate are interrelated for the tracks investigated and this is apparently also true for severe handling manoeuvres such as the double lane change. These observations suggest that roll angle is a suitable metric to measure handling and that it can be used to determine the moment of switchover if limits of acceptability are set.