Actuation Patterns Research Articles

Identification of Handbrake Patterns of Young Motorcycle Riders in Thailand Using a Newly Invented Force Measuring Device

The paper aims at identifying handbrake control behavior of young Thai volunteer riders by focusing on small underbone-type of motorcycle using a newly developed force measuring device. The device has been invented to measure the handbrake force using the potentiometer through the fulcrum of hand control lever. Through calibration with the discrete static loads, the relation between the rotational hand control lever and the handbrake force has been determined. This technique is applicable for both hydraulic or cable handbrake systems. It has been employed to measure each rider’s handbrake force against both handbrake levers during brake application. Our sample included thirty volunteers and a professional rider. We conducted the tests based on transportation standard regulation of the United Nations Economic Commission for Europe (UNECE) regulation No. 78, under speed of 40 km/hr. Three types of handbrake patterns have been identified from these tests. Consequently, the force response characteristics from hydraulic and cable systems in motorcycle are notably different. The number of rider’s finger actuation and various patterns applied at the hand brake levers have been revealed to improve the brake skill from young motorcyclists.

Fault-Tolerant Electro-Responsive Surfaces for Dynamic Micropattern Molds and Tunable Optics

Electrically deformable surfaces based on dielectric elastomers have recently demonstrated controllable microscale roughness, ease of operation, fast response, and possibilities for programmable control. Potential applications include marine anti-biofouling, dynamic pattern generation, and voltage-controlled smart windows. Most of these systems, however, exhibit limited durability due to irreversible dielectric breakdown. Lowering device voltage to avoid this issue is hindered by an inadequate understanding of the electrically-induced wrinkling deformation as a function of the deformable elastic film thickness. Here we report responsive surfaces that overcome these shortcomings: we achieve fault-tolerant behavior based on the ability to self-insulate breakdown faults, and we enhance fundamental understanding of the system by quantifying the critical field necessary to induce wrinkles in films of different thickness and comparing to analytical models. We also observe new capabilities of these responsive surfaces, such as field amplification near local breakdown sites, which enable actuation and wrinkle pattern formation at lower applied voltages. We demonstrate the wide applicability of our responsive, fault-tolerant films by using our system for adjustable transparency films, tunable diffraction gratings, and a dynamic surface template/factory from which various static micropatterns can be molded on demand.

LQG-Based Control and Scheduling Co-Design

Control and scheduling co-design becomes an issue when several controller tasks share the same execution platform and disrupt the ideal sampling and actuation patterns. In co-design the objective is to optimize the combined performance of all the controllers on the platform, subject to schedulability constraints. In the paper four LQG-based co-design methods are reviewed and evaluated: delay-aware, stochastic, periodic, and harmonic LQG co-design.

Individually Controllable Magnetic Cilia: Mixing Application

This paper introduces a new design for individually controlled magnetic artificial cilia for use in fluid devices and specifically intended to improve the mixing in DNA microarray experiments. The design has been implemented using a low-cost prototype that can be fabricated using polydimethylsiloxane (PDMS) and off-the-shelf parts and achieves large cilium deflections (59% of the cilium length). The device's performance is measured via a series of mixing experiments using different actuation patterns inspired by the blinking vortex theory. The experimental results, quantified using the relative standard deviation of the color when mixing two colored inks, show that exploiting the individual control leads to faster mixing (38% reduction in mixing time) than when operating the device in a simultaneous-actuation mode with the same average cilium beat frequency. Furthermore, the experimental results show an optimal beating pattern that minimizes the mixing time. The existence and character of this optimum is predicted by simulations using a blinking-vortex approach for 2D ideal flow, suggesting that the blinking-vortex model can be used to predict the effect of parameter variation on the experimental system.

Encoding and presentation of surface textures using a mechanotactile display

Tactile displays can present virtual tactile sensations to the user by stimulating tactile receptors, which are distributed spatially within the skin and are classified into four types based on their characteristic temporal pattern of impulses. The mechanotactile displays can stimulate different types of the receptors selectively by changing the displacement and frequency of the skin deformation. In our previous work, we developed an array of large-displacement microactuators composed of hydraulic amplification mechanism (HDAM) and piezoelectric actuators, which is capable of stimulating all the four types of the tactile receptors. We controlled the driving parameters that were the driving voltage, vibration frequency, and actuation patterns of the actuators, and successfully presented various surface textures. However, in practical applications, the control parameters are to be tuned according to the surface textures that we want to present. In addition, the input signals to the piezoelectric actuators would consist of multiple frequency components and are difficult to create through trial and errors. To solve this inverse problem, in this work, we encoded the sample surface textures to voltage signals by sliding the sample over the HDAM and using the piezoelectric actuators as sensors. First, we attempted to reproduce the surface textures. The encoded signals were amplified to drive the mechanotactile display. The perception tests indicated that this approach was effective. Secondly, we attempted to correlate the encoded signals with hardness of the samples. The encoded signals were investigated among the samples of different hardness. In addition, we fabricated moicropatterned tactile samples that have the same physical properties except Young’s modulus to isolate hardness from other parameters. The encoded signals were compared to extract the characteristic signals to determine the hardness. These signals were used to drive the tactile display in the perception tests, which verified the effectiveness of the approach. These two approaches that were proposed and experimentally verified in this paper are readily applicable to solve the inverse problem in tactile display applications.

Learnability of the Moving Surface Profiles of a Soft Robotic Sorting Table

This paper analyzes the application of machine learning techniques to the control of a soft, peristaltic, $xy$ -sorting table. In particular, we address peristaltic tables made of a soft upper silicone layer and actuated by an array of integrated air-filled chambers. The chambers are pneumatically inflated in order to deform the table and move objects on the table. To control the robot precisely, it is necessary to model both the inverse mapping between the control signals of the actuators and the resulting surface deformation. There is currently no parametric model available. In this paper, we, therefore, study if nonparametric approaches are applicable. In these approaches, the mapping would be learned from a database of input signals and observed behaviors. From our analysis, we conclude that the most promising research direction consists in the nonparametric modeling of a limited set of peristaltic actuation patterns. However, the nonlinear hardware design that impedes a parametric model also affects the nonparametric optimization process. Our simulation suggests that the optimization is nonconvex, approximately monotonous, and feasible in terms of the number of observations of the physical robot.

Design and Modeling of Flexible Passive Rowing Joint for Robotic Fish Pectoral Fins

Paired pectoral fins that are capable of rowing motions are an important actuation mechanism for robotic fish. Existing work in this area typically adopts a rigid connection between the actuator and the pectoral fins, which requires a faster actuation speed in the power stroke than in the recovery stroke to produce a net thrust or moment. In addition to increasing the control complexity, the latter requirement leads to slow robot speeds due to prolonged deceleration during the recovery stroke. In this paper, we propose the design of a novel flexible passive joint that connects the servomotor arm to the pectoral fin, to overcome the aforementioned problem. A dynamic model is developed for the joint and for a robotic fish equipped with such joints. The design and the model are evaluated with extensive experimental results. With symmetric actuation patterns during the power and recovery strokes, the robotic fish with the proposed joints shows clear speed advantage over the case involving rigid joints and asymmetric actuation. Motivated by the need for design optimization, the model is further utilized to investigate the influence of the joint length and stiffness on the robot locomotion performance and efficiency. It is found that, for low fin-beat frequencies, longer or more flexible joints lead to higher speeds, and the trend is reversed at high fin-beat frequencies. On the other hand, while the mechanical efficiency shows a decreasing trend when the frequency increases, it is higher with shorter joints. These findings suggest the utility of the proposed model for multiobjective design of the joint and its operating frequency.

Surface properties that can be displayed by a microelectromechanical system‐based mechanical tactile display

This study reports the surface properties that a microelectromechanical system (MEMS)-based mechanical tacitle display can present. The display is composed of 3 by 3 large displacement MEMS actuators that comprise hydraulic displacement amplification mechanism and piezoelectric actuators. The control parameters of the display include the displacement, or driving voltage, vibration frequency, and spatial and temporal actuation patterns of the actuators. Roughness and hardness using the newly proposed sample comparison method have been investigated previously. In this study, methods investigating warmness, or thermal conductivity, wettability, or surface energy, and friction were considered. Correlation between the control parameters and the surface properties indicated that the mechanical tactile display is best at controlling the roughness of the surface.

Dynamical analysis and design of active orthoses for spinal cord injured subjects by aesthetic and energetic optimization

The dynamic analysis and simulation of human gait using multibody dynamics techniques has been a major area of research in the last decades. Nevertheless, not much attention has been paid to the analysis and simulation of robotic-assisted gait. Simulation is a very powerful tool both for assisting the design stage of active rehabilitation robots and predicting the subject–orthoses cooperation and the resulting aesthetic gait. This paper presents a parameter optimization approach that allows simulating gait motion patterns in the particular case of a subject with incomplete spinal cord injury (SCI) wearing active knee–ankle–foot orthoses at both legs. The subject is modelled as a planar multibody system actuated through the main lower limb muscle groups. A muscle force-sharing problem is solved to obtain optimal muscle activation patterns. Furthermore, denervation of muscle groups caused by the SCI is parameterized to account for different injury severities. The active orthoses are modelled as external devices attached to the legs, and their dynamic and performance parameters are taken from a real prototype. Numerical results using energetic and aesthetic objective functions, and considering different SCI severities are obtained. Detailed discussions are given related to the different motion and actuation patterns both from muscles and orthoses. The proposed methodology opens new perspectives towards the prediction of human-assisted gait, which can be very helpful for the design of new rehabilitation robots.

Adding adaptable toe stiffness affects energetic efficiency and dynamic behaviors of bipedal walking

In human walking, toes play an important role in supporting the body and controlling the forward motion. These functions are achieved by muscles and tendons around toe joints. To further understand the importance of toe and how toe muscle functions affect the locomotion, we employ a simple bipedal walking model with compliant joints. The ankle joints and toe joints are modeled as torsional springs and the actuation patterns are similar to that of normal human walking. Experimental results show that adding adaptable compliant toe joints could benefit the stability and energy efficiency. By generating plantar flexion moment after heel-off, the toes contribute to stabilize the body and control the forward motion. In addition, multi-joint foot structure could improve the energy efficiency by reducing the energy consumption of ankle joints. A proper toe actuation pattern could result in a proper toe dorsiflexion and reduce the maximal ankle plantar flexion, leading to a smoother and more efficient locomotion.

Modelling cephalopod-inspired pulsed-jet locomotion for underwater soft robots

Cephalopods (i.e., octopuses and squids) are being looked upon as a source of inspiration for the development of unmanned underwater vehicles. One kind of cephalopod-inspired soft-bodied vehicle developed by the authors entails a hollow, elastic shell capable of performing a routine of recursive ingestion and expulsion of discrete slugs of fluids which enable the vehicle to propel itself in water. The vehicle performances were found to depend largely on the elastic response of the shell to the actuation cycle, thus motivating the development of a coupled propulsion-elastodynamics model of such vehicles. The model is developed and validated against a set of experimental results performed with the existing cephalopod-inspired prototypes. A metric of the efficiency of the propulsion routine which accounts for the elastic energy contribution during the ingestion/expulsion phases of the actuation is formulated. Demonstration on the use of this model to estimate the efficiency of the propulsion routine for various pulsation frequencies and for different morphologies of the vehicles are provided. This metric of efficiency, employed in association with the present elastodynamics model, provides a useful tool for performing a priori energetic analysis which encompass both the design specifications and the actuation pattern of this new kind of underwater vehicle.

Simulation-Based Design for Wearable Robotic Systems: An Optimization Framework for Enhancing a Standing Long Jump.

Technologies that augment human performance are the focus of intensive research and development, driven by advances in wearable robotic systems. Success has been limited by the challenge of understanding human-robot interaction. To address this challenge, we developed an optimization framework to synthesize a realistic human standing long jump and used the framework to explore how simulated wearable robotic devices might enhance jump performance. A planar, five-segment, seven-degree-of-freedom model with physiological torque actuators, which have variable torque capacity depending on joint position and velocity, was used to represent human musculoskeletal dynamics. An active augmentation device was modeled as a torque actuator that could apply a single pulse of up to 100 Nm of extension torque. A passive design was modeled as rotational springs about each lower limb joint. Dynamic optimization searched for physiological and device actuation patterns to maximize jump distance. Optimization of the nominal case yielded a 2.27m jump that captured salient kinematic and kinetic features of human jumps. When the active device was added to the ankle, knee, or hip, jump distance increased to between 2.49 and 2.52m. Active augmentation of all three joints increased the jump distance to 3.10m. The passive design increased jump distance to 3.32m by adding torques of 135, 365, and 297 Nm to the ankle, knee, and hip, respectively. Dynamic optimization can be used to simulate a standing long jump and investigate human-robot interaction. Simulation can aid in the design of performance-enhancing technologies.

Optimized actuators for ultrathin deformable primary mirrors.

A novel design and selection scheme for surface-parallel actuators for ultrathin, lightweight mirrors is presented. The actuation system consists of electrodes printed on a continuous layer of piezoelectric material bonded to an optical-quality substrate. The electrodes provide almost full coverage of the piezoelectric layer, in order to maximize the amount of active material that is available for actuation, and their shape is optimized to maximize the correctability and stroke of the mirror for a chosen number of independent actuators and for a dominant imperfection mode. The starting point for the design of the electrodes is the observation that the correction of a figure error that has at least two planes of mirror symmetry is optimally done with twin actuators that have the same optimized shape but are rotated through a suitable angle. Additional sets of optimized twin actuators are defined by considering the intersection between the twin actuators, and hence an arbitrarily fine actuation pattern can be generated. It is shown that this approach leads to actuator systems with better performance than simple, geometrically based actuators. Several actuator patterns to correct third-order astigmatism aberrations are presented, and an experimental demonstration of a 41-actuator mirror is also presented.

A novel alternating current multiple array electrothermal micropump for lab-on-a-chip applications.

The AC electrothermal technique is very promising for biofluid micropumping, due to its ability to pump high conductivity fluids. However, compared to electroosmotic micropumps, a lack of high fluid flow is a disadvantage. In this paper, a novel AC multiple array electrothermal (MAET) micropump, utilizing multiple microelectrode arrays placed on the side-walls of the fluidic channel of the micropump, is introduced. Asymmetric coplanar microelectrodes are placed on all sides of the microfluidic channel, and are actuated in different phases: one, two opposing, two adjacent, three, or all sides at the same time. Micropumps with different combinations of side electrodes and cross sections are numerically investigated in this paper. The effect of the governing parameters with respect to thermal, fluidic, and electrical properties are studied and discussed. To verify the simulations, the AC MAET concept was then fabricated and experimentally tested. The resulted fluid flow achieved by the experiments showed good agreement with the corresponding simulations. The number of side electrode arrays and the actuation patterns were also found to greatly influence the micropump performance. This study shows that the new multiple array electrothermal micropump design can be used in a wide range of applications such as drug delivery and lab-on-a-chip, where high flow rate and high precision micropumping devices for high conductivity fluids are needed.

Locomotion of inchworm-inspired robot made of smart soft composite (SSC)

A soft-bodied robot made of smart soft composite with inchworm-inspired locomotion capable of both two-way linear and turning movement has been proposed, developed, and tested. The robot was divided into three functional parts based on the different functions of the inchworm: the body, the back foot, and the front foot. Shape memory alloy wires were embedded longitudinally in a soft polymer to imitate the longitudinal muscle fibers that control the abdominal contractions of the inchworm during locomotion. Each foot of the robot has three segments with different friction coefficients to implement the anchor and sliding movement. Then, utilizing actuation patterns between the body and feet based on the looping gait, the robot achieves a biomimetic inchworm gait. Experiments were conducted to evaluate the robot’s locomotive performance for both linear locomotion and turning movement. Results show that the proposed robot’s stride length was nearly one third of its body length, with a maximum linear speed of 3.6 mm s−1, a linear locomotion efficiency of 96.4%, a maximum turning capability of 4.3 degrees per stride, and a turning locomotion efficiency of 39.7%.

Design and experiment of a compact wrist mechanism with high torque density

This paper proposes a new wrist mechanism for robot manipulation. To develop multi-DOF wrist mechanisms that can emulate human wrists, compactness and high torque density are the major challenges. Traditional approaches use a series of rotary motors that require gearing to amplify the output torque. This often results in an oversized wrist. Alternatively, large linear force can be easily attained in a compact space by using leadscrew motors. Inspired by the muscle–tendon actuation pattern, the proposed mechanism consists of two parallel placed linear motors. Their translational motions are transmitted to two perpendicular axes of rotation through a spherical mechanism and two slider crank mechanisms. A high torque density can be achieved. Static and dynamic models are developed to design and analyze the wrist mechanism. Experiments of a wrist prototype are presented and the results are discussed. The novel mechanism is lightweight and has a humanlike appearance. It is expected to serve as a basis to develop humanoid manipulators for human-friendly interactions.

Sample preparation with multiple dilutions on digital microfluidic biochips

Digital microfluidic (DMF) biochips offer a versatile platform for implementing several laboratory based biochemical protocols. These tiny chips can electrically control the dynamics of nanoliter volume of discrete fluid droplets on an electrode array by application of actuation patterns. One important step in biochemical sample preparation is dilution, where the objective is to prepare a fluid with a desired concentration factor. The protocols implemented on DMF biochips may require several different concentration values of a sample. In this study, the authors propose a scheme to produce such target droplets from a supply of an input sample and a buffer solution. Simulation results show a significant amount of savings in the number of mix-split steps and waste droplets in comparison to other methods for generating multiple concentration factors.

SPH BASED OPTIMIZATION OF ELECTROWETTING-DRIVEN DIGITAL MICROFLUIDICS WITH ADVANCED ACTUATION PATTERNS

Fast and thorough mixing is a crucial operation of digital microfluidic devices, where discrete and small fluid portions are moved and processed. In this paper, we want to analyze and to optimize the mixing process by substituting conventional motion and superposing oscillatory and translational modes. An accurate multiphase smoothed particle hydrodynamics (SPH) discretization for incompressible flow is instantiated. Different harmonic excitation patterns for the solid–liquid surface energy are applied and their influence on droplet mode shapes, formation of eddies and the Shannon entropy of droplet fluid components are measured. We tailor enhanced actuation patterns which improve mixing grade and reduce mixing time.

5PM3-PMN-041 触覚ディスプレイのための表面形状の符号化(ヒューマンインターフェース,ポスターセッション)

Our group demonstrated a MEMS-based tactile display that can control the created surface textures by the driving frequency and voltage of the actuators. It can create rough or smooth surfaces, but so far it is not successful to control the characteristics of the created surfaces that include roughness, hardness, etc. This paper attempted to obtain the actuation patterns of MEMS tactile display to create a designated surface textures. In order to do so, we slide the surface on the tactile display, consisting of an array of piezoelectric actuators, and detect the generated voltages by the actuators. The ultimate goal of this work is to code the surface textures into frequency and voltage.

TowardsPhysarumEngines

The slime mouldPhysarumpolycephalumis a suitable candidate organism for soft-matter robotics because it exhibits controllable transport, movement and guidance behaviour.Physarummay be considered as a smart computing and actuating material since both its motor and control systems are distributed within its undifferentiated tissue and can survive trauma such as excision, fission and fusion of plasmodia. Thus it may be suitable for exploring the generation and distribution of micro-actuation in individual units or planar arrays. We experimentally show how the plasmodium ofPhysarumis shaped to execute controllable oscillatory transport behaviour applicable in small hybrid engines. We measure the lifting force of the plasmodium and demonstrate how protoplasmic transport can be influenced by externally applied illumination stimuli. We provide an exemplar vehicle mechanism by coupling the oscillations of the plasmodium to drive the wheels of a Braitenberg vehicle and use light stimuli to effect a steering mechanism. Using a particle model ofPhysarumwe show how emergent travelling wave patterns produced by competing oscillatory domains may be used to to generate spatially represented actuation patterns. We demonstrate different patterns of controllable motion, including linear, reciprocal, rotational and helical, and demonstrate in simulation how dynamic oscillatory patterns may be translated into motive forces for simple transport of substances within a patterned environment.