Binary Actuators Research Articles

Design of a mobile binary parallel robot that exploits nonsingular transitions

Sliding-frame mobile robots used for autonomously inspecting metallic structures consist of two bodies connected by few joints. They move by alternately adhering one body to the structure while moving the other body to the next position. Sliding-frame robots are simpler and offer safer adhesion than legged and wheeled robots, and their control can be simplified using binary actuators that adopt only two stable states. However, most existing sliding-frame robots require continuous actuators to reach targets with precision, since binary actuators impose steps of fixed length. To solve this, this paper presents a new sliding-frame robot consisting of two bodies connected through a 2RPR-PR kinematic chain driven by two binary actuators. The 2RPR-PR chain can perform nonsingular transitions, which is the ability of many parallel robots to switch between different poses corresponding to the same state of its actuators, without crossing singularities. Thanks to this, the poses reachable by the proposed robot are doubled, granting it a denser workspace and more accuracy than similar robots, using only two binary actuators. The feasibility of the proposed robot is shown through a prototype.

A Kinematic Coupling Mechanism With Binary Electromagnetic Actuators for High-Precision Positioning

Rather than working in a continuous range of motion, binary actuators can only maintain two positions. This lack of flexibility is compensated by high accuracy, repeatability, and reliability. These features make binary-actuated mechanisms appealing for space exploration systems, repetitive pick and place tasks, and biomedical applications. This article introduces a novel class of binary-actuated mechanisms driven by electromagnets. As these systems rely on the extreme positions of their binary actuators for positioning, the proposed design aims to increase repeatability with a kinematic coupling. By inverting the polarity of its electromagnets, the configuration of the mechanism can be changed from a discrete state to another one. Thus, when the actuation is known, the pose of the system can be accurately computed without any external feedback. A sensorless design simplifies both the control and the architecture of the proposed design, as well as reducing manufacturing and maintenance costs. The conceptual design of the proposed class of mechanisms is described through two examples with three and four configurations, and alternative designs with higher mobility are discussed. Then, a kinematic synthesis procedure is discussed. Finally, the advantages of asymmetric and irregular designs are outlined. Overall, the proposed mechanisms are suited to a wide range of applications that require a rapid, accurate, and interchangeable positioning of sensors and tools.

Adaptive and distributed operation of HVAC systems: Energy and comfort implications of active diffusers as new adaptation capacities

Human-aware HAVC operations have been shown to be effective in improving energy efficiency, which is constrained by the HVAC system configuration and operational logic. These constraints can result in a lack of operational flexibility, which in turn reduces the adaptation capacity for energy efficiency. Therefore, in this study, we investigated the energy efficiency implications of novel adaptive capacities for HVAC including the use of proposed active diffusers, which add to the dynamics of the HAVC systems by adjusting the behavior of diffusers using two modalities of (1) binary actuation of air flow (turning flow on and off), and (2) adjusting the flow direction to target individual needs in an environment. Computational fluid dynamics was used to model and simulate the behavior of a “real-world” thermal zone to evaluate five scenarios of adaptive operations using distributed feedback from the environment, as well as active diffusers. Three scenarios used binary actuation at the thermal zone (collection of rooms) level, and two examined the adaptive operations at the diffusers level. Moreover, we examined the integration of distributed feedback at occupant locations into the control loop using averaged temperatures (in the first three scenarios) and individual-level feedback (in scenarios with diffuser level actuation). The coupling of distributed feedback and independent directional flow at the diffuser level considerably improved thermal comfort while reducing energy demands by ~25%—reflecting a considerable impact on improved energy efficiency. These findings demonstrate the potentials that artificial intelligence frameworks could bring about by enabling autonomous adaptive operations.

Electronics-Free Logic Circuits for Localized Feedback Control of Multi-Actuator Soft Robots

The vision of creating entirely-soft robots capable of performing complex tasks will be accomplished only when the controllers required for autonomous operation can be fully implemented using soft components. Despite recent advances in compliant fluidic circuitry for mechanical signal processing, the applicability of this technology for soft robot control has been limited by complicated fabrication and tuning processes, and also the need for external signals such as clocks and digital references. We propose a method to develop pneumatic soft robots in which coordinated interactions between multiple actuators are performed using controllers implemented on components distributively embedded in the soft structures of the system. In this approach, the notions of binary and multi-valued actuator logic states are introduced. In this way, the physical local dynamical couplings between the analog states of the actuators, established using soft valves of a new type, can be thought of as logic-gate-based mappings acting on discretized representations of the actuator states. Consequently, techniques for digital logic design can be applied to derive the architectures of the localized mechanical couplings that intelligently coordinate the oscillation patterns of the actuator responses. For the purposes of controller tuning, the soft valves are conceived so that their main physical parameters can be adjusted from the exterior of the robot through simple geometrical changes of the corresponding structural elements. To demonstrate the proposed approach, we present the development of a six-state locomoting soft robot.

Experimental characterization of a binary actuated parallel manipulator

This paper describes the BAPAMAN (Binary Actuated Parallel MANipulator) series of parallel manipulators that has been conceived at Laboratory of Robotics and Mechatronics (LARM). Basic common characteristics of BAPAMAN series are described. In particular, it is outlined the use of a reduced number of active degrees of freedom, the use of design solutions with flexural joints and Shape Memory Alloy (SMA) actuators for achieving miniaturization, cost reduction and easy operation features. Given the peculiarities of BAPAMAN architecture, specific experimental tests have been proposed and carried out with the aim to validate the proposed design and to evaluate the practical operation performance and the characteristics of a built prototype, in particular, in terms of operation and workspace characteristics.

Trajectory Planning for Micromanipulation With a Nonredundant Digital Microrobot: Shortest Path Algorithm Optimization With a Hypercube Graph Representation

Microrobotics is an ongoing study all over the world for which design is often inspired from macroscale robots. We have proposed the design of a new kind of microfabricated microrobot based on the use of binary actuators in order to generate a highly accurate and repeatable tool for positioning tasks at microscale without any sensor (with open-loop control). Our previous work consisted in the design, modeling, fabrication, and characterization of the first planar digital microrobot. In this paper, we focus on the motion planning of this robot for micromanipulation tasks. The complex motion pattern of this robot requires the use of algorithms. Graph theory is well suited for the discrete workspace generated by this robot. The comparison between several well-known trajectory-planning algorithms is done. A new graphical representation, named the hypercubic graph, is used for improving the computation speed of the algorithm. This is particularly useful for large workspace robots.

Design and Implementation of a Binary Redundant Manipulator With Cascaded Modules1

The subject of this paper is the design and implementation of a prototype snakelike redundant manipulator. The manipulator consists of cascaded modules eventually forming a macroscopically serial robot and is powered by shape memory alloy (SMA) wires. The SMAs (NiTi) act as binary actuators with two stable states and as a result, the repeatability of the manipulator's movement is ensured, alleviating the need for complex feedback sensing. Each module is composed of a customized spring and three SMA wires which form a tripod with three degrees of freedom (DOFs). Embedded microcontrollers networked with the I2C protocol activate the actuators of each module individually. In addition, we discuss certain design aspects and propose a solution that deals with the limited absolute stroke achieved by SMA wires. The forward and inverse kinematics of the binary manipulator are also presented and the tradeoff between maneuverability and computational complexity is specifically addressed. Finally, the functionality and maneuverability of this design are verified in simulation and experimentally.

Three-dimensional construction and omni-directional rolling analysis of a novel frame-like lattice modular robot

Lattice modular robots possess diversity actuation methods, such as electric telescopic rod, gear rack, magnet, robot arm, etc. The researches on lattice modular robots mainly focus on their hardware descriptions and reconfiguration algorithms. Meanwhile, their design architectures and actuation methods perform slow telescopic and moving speeds, relative low actuation force verse weight ratio, and without internal space to carry objects. To improve the mechanical performance and reveal the locomotion and reconfiguration binary essences of the lattice modular robots, a novel cube-shaped, frame-like, pneumatic-based reconfigurable robot module called pneumatic expandable cube(PE-Cube) is proposed. The three-dimensional(3D) expanding construction and omni-directional rolling analysis of the constructed robots are the main focuses. The PE-Cube with three degrees of freedom(DoFs) is assembled by replacing the twelve edges of a cube with pneumatic cylinders. The proposed symmetric construction condition makes the constructed robots possess the same properties in each supporting state, and a binary control strategy cooperated with binary actuator(pneumatic cylinder) is directly adopted to control the PE-Cube. Taking an eight PE-Cube modules’ construction as example, its dynamic rolling simulation, static rolling condition, and turning gait are illustrated and discussed. To testify telescopic synchronization, respond speed, locomotion feasibility, and repeatability and reliability of hardware system, an experimental pneumatic-based robotic system is built and the rolling and turning experiments of the eight PE-Cube modules’ construction are carried out. As an extension, the locomotion feasibility of a thirty-two PE-Cube modules’ construction is analyzed and proved, including dynamic rolling simulation, static rolling condition, and dynamic analysis in free tipping process. The proposed PE-Cube module, construction method, and locomotion analysis enrich the family of the lattice modular robot and provide the instruction to design the lattice modular robot.

Influence Vectors Control for Robots Using Cellular-Like Binary Actuators

Robots using cellular-like redundant binary actuators could outmatch electric-gearmotor robotic systems in terms of reliability, force-to-weight ratio, and cost. This paper presents a robust fault-tolerant control scheme that is designed to meet the control challenges that are encountered by such robots, i.e., discrete actuator inputs, complex system modeling, and cross-coupling between actuators. In the proposed scheme, a desired vectorial system output, such as a position or a force, is commanded by recruiting actuators based on their influence vectors on the output. No analytical model of the system is needed; influence vectors are identified experimentally by sequentially activating each actuator. For position control tasks, the controller uses a probabilistic approach and a genetic algorithm to determine an optimal combination of actuators to recruit. For motion control tasks, the controller uses a sliding mode approach and independent recruiting decision for each actuator. Experimental results on a four degrees of freedom binary manipulator with 20 actuators confirm the method’s effectiveness and its ability to tolerate massive perturbations and numerous actuator failures.

Gait fitting for snake robots with binary actuators

Thanks to the special physical architectures and various locomotion gaits, snake robots may offer significant benefits over traditional legged or wheeled locomotion designs in vast types of scenarios. This paper proposes an innovative snake robot with digitally-actuated Stewart platforms as its modules and mainly focuses on the simulations of various snake gaits. Three categories of fitting algorithms are elaborated in simulations of lateral undulation and Configuration-Fitting Algorithm of Four Modules is demonstrated as a universal gait fitting algorithm for all kinds of snake robots with binary actuators. Several typical snake gaits are simulated and the results demonstrate the excellent mobility of the snake robot.

A Novel Deployable Hexahedron Mobile Mechanism Constructed by Only Prismatic Joints

This paper proposes a novel deployable hexahedron mobile mechanism that is rigidly linked by only prismatic joints. The mechanism that is a completely symmetrical structure can always keep the walking capability when any of its six faces of the hexahedron touches the ground. It can roll at any stable state. The configuration constructed by only prismatic joints makes it expand and contract as a deployable structure. In this paper, a method for constructing a deployable hexahedron mobile mechanism is proposed. The stability analysis and dynamic simulation of the walking and rolling are carried out. The necessary condition of tipping motion and the speed analysis of two different rolling gaits are studied in details. A binary control strategy is adopted to simplify the complexity of the control system. A pneumatic cylinder is chosen to be the binary actuator. A prototype composed of 180 pneumatic cylinders was fabricated. The validity of the walking and tipping functions are verified by the experimental results.

Design and control strategies for SMA actuators in a feed axis for precision machine tools

In a current project, the Chair of Production Systems (LPS) is examining the use of standardized shape memory alloy (SMA) actuators in the feed axis of a small machine tool. These machines are used to manufacture small work pieces with high precision. Therefore, the actuators must be qualified to handle movements in the micrometer range. To achieve this goal, different design elements for the actuators are considered, as well as different measures to control the actuator. In the scope of this paper, binary actuators with just two possible positions are examined next to actuators that can reach every possible intermediate position. For the latter, different control strategies are proposed. The displacement of the actuators can either be measured by external sensors or by using the change in resistance in the SMAs during transformation as feedback.

A modular design kit for task-adaptable low-cost robots based on BaPaMan design

This paper discusses the redesign of a binary parallel manipulator named BaPaMan (Binary Actuated Parallel Manipulator). The aim of this work is the improvement of the structures stiffness of BaPaMan. Additionally this paper shows the implementation of a construction kit which allows task-adaptation of low-cost robots based on the BaPaMan structure. BaPaMan is a three degree of freedom (DOF) spatial parallel robot which comprises flexure hinges and Shape Memory Alloy (SMA) actuators to achieve a low-cost design, well suited for easy operation applications. Measurements have shown that this comes at the cost of poor structural stiffness and end effector accuracy. To counter these issues BaPaMan2 and BaPaMan3 have been developed and are elaborated within this work. During the design phase, an empirical FEA is used to improve the flexure hinge performance, which analyses relations between several design parameters and the stiffness of the entire system. Finally, task-adaptation is achieved by using a design methodology and a parametric CAD model for BaPaMan. Besides the paper introduces first applications of the BaPaMan structure and shows future work.

The conceptual design of a spatial binary hyper redundant manipulator and its forward kinematics

The hyper redundant manipulators (HRMs) have excessively many degrees of freedom. As a special but practicable subset of them, the binary hyper-redundant manipulators (BHRMs) use binary (on–off) actuators with only two stable states such as pneumatic cylinders and/or solenoids. This article describes the conceptual design of a spatial BHRM together with its forward kinematics. This BHRM consists of many modules with the same constructive characteristics. The modules increase in size from the tip to the base so that the actuator powers also increase in the same order. Each module consists of three submodules. The first and second submodules have the shapes of variable geometry trusses and they work in mutually orthogonal planes. The third submodule is a discrete twister. The manipulator is assumed to be driven by pneumatic on–off actuators. Because of the discrete nature of the on–off actuators, a small but continuously actuated six-joint manipulator is installed as the last module of the BHRM in order to compensate the discretization errors.

Mechatronic Design of a Shape Memory Alloy Actuator for Automotive Tumble Flaps: A Case Study

The continuous advance in mechatronics has long attracted researchers toward the development of new highly integrated actuators for automotive applications where reduced space and low weight are common constraints. In this context, Shape Memory Alloys (SMAs) offer many peculiar characteristics that make this technology very attractive for the construction of miniature mechatronic actuators. This paper presents the design, the prototype fabrication, and the functional testing of a case study, where an SMA binary actuator is used for automotive tumble flaps. The innovative solid-state actuation system is proposed as an alternative to electromagnetic and pneumatic effectors, traditionally used to drive the tumble shaft of an air intake manifold for internal combustion engines. Original features of the linear actuator involve the mechanical architecture and the control structure. On the mechanical side, two contrasting sets of SMA springs are used to actively generate the net actuating force during both out-stroke and in-stroke. On the control side, a current feedback is exploited for sensorless real-time monitoring of the working temperature of the SMA springs during electrical supply. Major shortcomings of the proposed solution are a low response time and a power consumption higher than pneumatic and electromagnetic counterparts.

Nonautonomous Elementary Net Systems and Their Application to Programmable Logic Control

In this paper, a novel approach to Petri net modeling of programmable logic controller (PLC) programs is presented. The modeling approach is a simple extension of elementary net systems, and a graphical design tool that supports the use of this modeling approach is provided. A key characteristic of the model is that the binary sensory inputs and binary actuation outputs of the PLC are explicitly represented. This leads to the following two improvements: outputs are unambiguous, and interaction patterns are more clearly represented in the graphical form. The use of this modeling approach produces programs that are simple, lightweight, and portable. The approach is demonstrated by applying it to the development of a control module for a MonTech Positioning Station.

On the design of large degree-of-freedom digital mechatronic devices based on bistable dielectric elastomer actuators

Binary actuation has been proposed to reduce complexity in robotic and mechatronic systems. However, a relatively large number of binary actuators are required to achieve the accuracy necessary for practical applications. Conventional actuators are not practical for such large degree-of-freedom (DoF) devices. Here, a dielectric elastomer (DE) actuator is developed for these applications. It is shown that DE actuators have high energy densities, light weight, low cost, and large displacements. Hence they could potentially make large DoF binary systems practical. DE actuators proposed here consist of thin electrically sensitive elastomer films that are mounted in a flexible frame that incorporates a passive bistable element. The frame prestrains the film and provides a restoring force that allows the actuator to operate bidirectionally. A simple experimental prototype 6-DoF binary manipulator demonstrates the concept

Po-Thur Eve General-33: Feasibility of a Multileaf Collimator and Method for Multi-slice Tomotherapy

Purpose: Current methods for delivery of serial or helical tomotherapy are based on a collimator design which can, at most, irradiate two slices simultaneously as the source rotates around the patient. We investigate the feasibility of a novel multileaf collimator design and method for multi‐slice tomotherapy. Method and Materials: The MLC incorporates a compact pivoting leaf design. Intensity modulation is achieved through binary actuation of adjacent leaves. Multiple leaf banks are employed for multi‐slice tomotherapy delivery. Each fan beam will have a different divergence in the axial direction. Two multi‐slice delivery methods are evaluated where (a) pitch is determined by a given collimated slice which does not irradiate beyond the adjacent slice (regular pitch) or (b) pitch is determined by different collimated slices irradiating the same region in the patient (multi‐slice pitch). Junctioning effects were studied for a cylindrical phantom irradiated with open (unmodulated) fan beams. Results: A prototype MLC leaf has been tested which can switch between open and closed positions in a few tens of milliseconds. Regular pitch delivery produced the greatest inhomogeneity between regions irradiated by different collimated slices. The proposed multi‐slice pitch delivery method avoids regular pitch junctioning effects by irradiating all areas with all collimated slices. Conclusions: These results indicate that multi‐slice tomotherapy is feasible with the benefits of shorter treatment times and it may allow for the use of Co‐60 as a tomotherapy radiation source. Conflict of Interest: Research was supported in part through a licensing agreement with TomoTherapy Inc.

SU‐FF‐T‐336: Multi‐Slice Tomotherapy Delivery Methods Using a Novel Multileaf Collimator

Purpose: In this study, we present an initial dosimetric investigation of multi‐slice tomotherapy delivery methods using a novel multileaf collimator design. Method and Materials: A compact multileaf collimator design for multi‐slice tomotherapy is under investigation. Intensity modulation is achieved through binary actuation of adjacent pivoting leaves with multiple leaf banks employed to deliver multi‐slice tomotherapy. Pitch may be determined by the ratio of the couch travel distance for a complete gantry rotation divided by the slice width at the axis of rotation. For multi‐slice tomotherapy the concept of pitch is complicated by the use of multiple collimated slices and differing fan beam divergences. We have studied the dosimetric effect of: (a) using regular pitch, where a given collimated slice does not irradiate beyond the adjacent slice and (b) using multi‐slice pitch, where different collimated slices irradiate the same region in the patient. Other novel aspects of tomotherapy delivery with the multi‐slice collimator are presented. Results: The multi‐slice pitch delivery method allows for treatment of extended volumes greater than the spacing between slices, without the junctioning effect of the regular pitch method. A pitch less than 1 may be achieved when considering irradiation from different collimated slices and is a determined by the slice spacing, slice width and couch travel. The difference in fan beam divergence in the axial direction may be clinically advantageous. Single‐slice techniques may also benefit from non‐coplanar delivery. Conclusions: A method for multi‐slice tomotherapy delivery is investigated. Dosimetric results are presented for various methods of dose delivery including a multi‐slice pitch method for extended treatment lengths. Multi‐slice delivery will result in shorter treatment times for both linac and cobalt‐based tomotherapy systems and development of novel radiation therapy techniques. Conflict of Interest: Research was supported in part through a licensing agreement with TomoTherapy Inc.

Design and Evaluation of a Discretely Actuated Multi-Module Parallel Manipulator

In this paper, a new discretely actuated spatial parallel manipulator is presented as designed with binary pneumatic actuation. It has been used as a basic module for the construction of a multi-module parallel manipulator. Major benefits of discretely actuated manipulators are high repeatability, relatively low cost, and no need for feedback control. In addition, hyper-redundancy allows executing tasks even when some actuators fail. Binary actuators can have only two stable states denoted by (0) and (1). In this paper, kinematic and static analyses have been reported to obtain design constraints that have been used to build a first prototype. A performance evaluation is carried out and the prototype has been built for experimental tests.