Large Workspace Research Articles

Design and Performance Analysis of a Novel Group of Translational Parallel Robots for a Three-Axis Grinding Machine

There are limited parallel robots applicable to three-axis grinding machines due to the restricted reachable workspace originating from multiple kinematic chains with spatial kinematic joints. The parallel robot will gain significant potential in the industry if a larger workspace can be achieved. This research introduces a special relationship between upper triangular matrix and parallel robot structures for the purpose of designing a group of novel parallel robots without spatial kinematic joints. The detailed inverse kinematic solution of the selected parallel manipulator is derived in accordance with its straightforward architecture. Several singularity configurations are found on the basis of the first-order kinematic relation. The translational reachable workspace is close to a triangular prism. The dexterity and stiffness performances based on the Jacobian matrix are explored for the chosen parallel manipulator. Both indices display a downward trend as the mobile platform rises higher.

Personal Air Cleaning by a User-Tracking Robot Equipped with a Nanofiber Air Cleaner in a Large Work Space

Personal Air Cleaning by a User-Tracking Robot Equipped with a Nanofiber Air Cleaner in a Large Work Space

A Computational Approach for Internal Tendon Routing Channels in a Tendon-Driven Continuum Joint.

Tendon-driven continuum soft robots are currently applied in research and are given a promising perspective for future applications. For the routing of the tendons from the actuator to the point where the loading is demanded, two routing possibilities exist in the literature: internal routing of the tendons with the help of structurally embedded Bowden sheaths and external tendon routing where the tendon is not in contact with the soft structure. The application of the latter is a clear disadvantage for applications due to the high risk of interference with the tendon, for example, causing the tendon to break. The first option on the other hand introduces high friction forces into the tendon transmission and affects the elastic characteristic of the continuum and therefore the desired workspace of the system. This article overcomes the aforementioned problems by integrating tendon routings within tendon channels eroded from the continuum structure by a model-based design method. The channels within the continuum structure are computed a priori such that the tendons do not interact with the continuum while moving through its workspace. Overall, a new model-based method for tendon channel design is introduced and a corresponding manufacturing process is established. A continuum joint module prototype is designed to enable roll-pitch-yaw motions with a large accessible workspace. The capabilities of the system are measured in experiments using an external camera for the range of motion. Moreover, walking experiments on the ANYmal robot from ETHZ are presented.

Structural Design and Kinematic Analysis of Cable-Driven Soft Robot

Continuous robots have attracted more and more attention from the robotics community due to their high degree of flexibility and pliability, and have shown great potential for application in a variety of fields. With the continuous progress of material science, control technology, and artificial intelligence, the performance and application range of soft robotics have been further expanded, in which the cable drive has the advantages of large workspace, high flexibility, etc. The cable-driven soft robotic arm serves as an ultra-redundant robot that can operate in cramped and confined environments. In this paper, a cable-driven soft robot based on soft continuums and a cross gimbal is presented. The kinematics of the cable-driven soft robot is modeled and the mapping relations of the kinematics are solved by the D–H method and piecewise constant curvature, and the relations between the cable length, joint angle, and pose are further derived. Finally, the motion space of the cable-driven soft robot in the three-dimensional coordinate system is obtained by MATLAB2021b, and the single-segment soft body is simulated and analyzed using ADAMS to compare the theoretical data with the actual data and verify the reliability of this structure and method.

A robotic skill transfer learning framework of dynamic manipulation for fabric placement

Placing fabric poses a challenge to robots since fabric with high dimensional configuration space can deform during manipulation. Existing methods for placing fabric mostly rely on static operations, which are inefficient and require a large workspace. Therefore, this study applies dynamic manipulation (manipulating uncontrollable parts of the fabric by swinging) to fabric placement, proposing a novel learning framework for robotic dynamic fabric placement skill learning and generalization. The proposed framework integrates reinforcement learning with imitation learning, leveraging expert demonstration data to guide and accelerate skill acquisition. Additionally, fabric characteristics are combined with imitation learning to enable the transfer and generalization of the learned policy to real-world environments The experiments suggest that the proposed framework is capable of achieving the placement tasks for a range of positions and fabrics. For success rate, the policy of the proposed framework ultimately achieves a flatness of exceeding 95% and a placement distance error of less than 2 mm. Moreover, the proposed approach is similar in operation time to the fastest method, while it can reduce the space required for manipulating the fabric by over 15%. Compared with other placement policies, it is promising because of its high accuracy, flexibility, efficiency, as well as adaptability.

AR Digital Workspace: Extending the Workspace of a Mobile Device into Real Space

We propose AR Digital Workspace that extends the workspace of a mobile device in order to solve the narrow display area of mobile devices. The proposed interface allows a user to place multiple application windows on a flat surface in real space through a mobile device. The display area can be changed by moving the mobile device, allowing the user to easily switch between the applications. The user can change the positions and sizes of windows, operate applications in the windows, and copy and paste text between windows by touching the screen of the mobile device. The user can also copy characters in real space by recognizing characters in the images captured by the device’s camera. This interface allows the user to work with a large amount of information displayed in a large workspace. We conducted an experiment to compare the proposed interface with a traditional touchscreen interface using a task that involves switching between multiple applications to explore necessary information and answer questions ( N = 14 ). The results showed no difference in task completion time between the methods, but as trials were repeated, the completion time with the proposed method decreased, and on the last trial, the proposed method took significantly less time than the touchscreen interface. It was also shown that the proposed method was significantly less burdensome for more than half of the NASA-TLX items.

Configuration Design and Size Optimization of a High-Precision Novel Parallel Pointing Mechanism Based on Interference Separation

Pointing mechanism is widely used in aerospace field, and its pointing accuracy and stability have high requirements. The pointing mechanism will be affected by external interference when it works. In order to eliminate the impact of interference forces on the output accuracy of the mechanism, firstly, this paper proposes a design method for high-precision pointing mechanisms based on interference separation, aiming at the high-precision pointing requirements of pointing mechanisms. Based on the screw theory, a synthesis method for inner compensation mechanisms has been proposed. And a new type of double-layer parallel mechanism has been designed to compensate for interference forces. Then, the kinematics and dynamics of the mechanism are carried out. An evaluation index for compensating external interference forces is proposed. The interference compensation analysis is conducted for the pointing mechanism. The correctness of the proposed interference force compensation coefficient is verified. Finally, in order to find the optimal solution for the workspace and interference force compensation coefficient of the pointing mechanism, multi-objective optimization design of the structural parameters of the mechanism was carried out based on the particle swarm optimization algorithm. This provides a theoretical basis for the prototype design of the subsequent double-layer parallel mechanism. This double-layer parallel mechanism combines the advantages of large load-bearing capacity, large workspace, and high output accuracy. It can be better applied in the aerospace field where high-precision pointing and force interference compensation are integrated.

Parallel–Serial Robotic Manipulators: A Review of Architectures, Applications, and Methods of Design and Analysis

Parallel–serial (hybrid) manipulators represent robotic systems composed of kinematic chains with parallel and serial structures. These manipulators combine the benefits of both parallel and serial mechanisms, such as increased stiffness, high positioning accuracy, and a large workspace. This study discusses the existing architectures and applications of parallel–serial robots and the methods of their design and analysis. The paper reviews around 500 articles and presents over 150 architectures of manipulators used in machining, medicine, and pick-and-place tasks, humanoids and legged systems, haptic devices, simulators, and other applications, covering both lower mobility and kinematically redundant robots. After that, the paper considers how researchers have developed and analyzed these manipulators. In particular, it examines methods of type synthesis, mobility, kinematic, and dynamic analysis, workspace and singularity determination, performance evaluation, optimal design, control, and calibration. The review concludes with a discussion of current trends in the field of parallel–serial manipulators and potential directions for future studies.

Reconfigurable cable-driven parallel mechanism design: physical constraints and control

Abstract The cable-driven parallel mechanism (CDPM) is known as an interesting application in industry to pick and place objects owing to its advantages such as large workspaces. In addition to the advantages of this mechanism, there are some challenges to improving performance by considering constraints in different components, such as the behavior of cables, shape, size of the end effector and base, and model of pulleys and actuators. Moreover, the impact of online geometry reconfiguration must be analyzed. This paper demonstrates the impact of these constraints on the performance of reconfigurable CDPM. The methodology is based on the systematic review and meta-analysis guidelines to report the results. The databases used to find the papers are extracted from Scopus and Google Scholar, using related keywords. As a result, the impact of physical constraints on system performance is discussed. A total of 90 and 37 articles are selected, respectively. After removing duplicates and unrelated papers, 88 studies that met the inclusion criteria are selected for review. Even when considering the physical constraints in modeling the mechanism, simplifications in designing a model for the reconfigurable CDPM generate errors. There is a gap in designing high-performance controllers to track desired trajectories while reconfiguring the geometry, and the satisfaction of physical constraints needs to be satisfied. In conclusion, this review presents several constraints in designing a controller to track desired trajectories and improve performance in future work. This paper presents an integrated controller architecture that includes physical constraints and predictive control.

Exploration of the application of solar energy technology in the field of new energy vehicles

Due to the harsh effects of fossil fuels on the world, researchers are paying more attention to the application of new energy sources. This paper explores the possibility to support electric vehicles with solar energy by demonstrating the design of a solar cooling system and a solar parking lot in a large flat area and workspace. The use of solar energy in electric vehicles can help control some systems such as cooling systems. Solar panels are used in some large flat parking area to collect and invert solar energy for parking electric vehicles’ charging. Solar panels are able to help charge electric vehicles during the workday by setting them on the surface of working area. However, due to the limitations of solar energy, solar panels are very much in need of good weather and direct sunlight. Therefore, solar energy cannot be the only source to support other powered vehicles. In the future, developments in other areas such as inverters and converters, solar panels, and nanotechnology may make the use of solar energy in green energy vehicles possible.

Modeling and end vibration suppression of space manipulators based on structural flexibility

Abstract With the rising demand for more flexibility and larger workspaces in collaborative robots, rigid-flexible coupling robotic systems have garnered increasing attention. This study focuses on trajectory tracking and vibration suppression for RFCRSs operating in 3D space. The nonlinear coupling between angular joint positions and flexible structural displacement leads to complex vibration behaviors. To address this issue, the assumed mode method is employed to curve-fit the first-order modal shape of the flexible arm, resulting in a shape function. This approach simplifies the nonlinear infinite-dimensional dynamics of RFCRSs into a fourth-order dynamical system. The reference trajectory is planned using the polynomial programming method based on the established kinetic model. The reference trajectory is tracked with a model reference adaptive control (MRAC) method to reduce the robot end vibration. Finally, the effectiveness of the robot model reduction method and the associated control strategy is validated through a comparison with PD control and MRAC, which does not account for arm flexibility.

Modeling and Experimental Validation of a Cable-Driven Robot for 3D Printing Construction

Abstract Cable-driven robots are characterized by a large workspace, high speed and load-to-weight ratio, providing a new technology approach for large-scale autonomous 3D construction of lunar surface shelters. A novel deployable cable-driven construction 3D printer (CDCP) is developed in this study. Guiding pulleys and cable sagging are considered and modeled to improve the accuracy of the system. A fuzzy adaptive differential evolution PID (FDEPID) control is proposed to reduce end-effector motion errors in Cartesian space and thus improve printing quality and stability. Concentric and zigzag infill strategies are compared to optimize printing efficiency and infill effectiveness in path planning. Finally, experiments are carried out to validate the proposed FDEPID control and path planning strategies which demonstrate the great potential of the developed cable-driven printer in the construction of lunar architecture.

A Positioning and Tracking Performance–Enhanced Composite Control Algorithm for the Macro–Micro Precision Stage

In the macro–micro composite motion process, the macro stage achieves rapid motion in a large workspace, while the micro stage realizes precise positioning within a small displacement. The large-stroke and high-speed motion of the macro stage is influenced by nonlinear friction, overshooting, and vibrations, making it challenging to achieve rapid stabilization within the travel range of the micro stage, thereby impacting equipment operation efficiency. This paper proposes a composite controller structure designed to solve the fast point-to-point positioning of the macro stage driven by a linear motor and enhance the trajectory tracking performance of the stage. The proposed composite control algorithm (CCA) includes velocity feed-forward, gain-scheduled proportional integral differential (PID) control, and a plug-in repetitive control method. By employing a tracking differentiator, velocity feed-forward, and a gain-scheduled PID controller, the control algorithm can realize rapid stabilization and positioning for the macro stage. Through velocity feed-forward, gain-scheduled PID control, and a plug-in repetitive controller, the control algorithm can reduce the trajectory tracking error of the stage. Simulations and experimental studies of point response and sinusoidal trajectory tracking are carried out on a macro–micro stage to verify the effectiveness of the composite controller for the linear motor. The experimental results demonstrate that the proposed composite controller effectively reduces the macro stage’s settling time and overshoot, and improves the accuracy of sinusoidal trajectory tracking, which lays a foundation for submicron positioning accuracy in high-speed macro–micro motion stages.

Development of 3-USR Type Spatial 6-DOF Parallel Mechanism with Large Workspace—Proposal of 3-USR Mechanism and Design of Spherical 5-Link Mechanism to Replace Active Universal Pairs (U)—

In this paper, we present a 3-USR-type 6-degree-of-freedom (6-DOF) parallel mechanism characterized by an expansive workspace. This mechanism consists of three coupling chains, each comprising a universal pair (U), a spherical pair (S), and a rotational pair (R), in sequence from the stationary base. To achieve a large workspace, the three stationary universal pairs are designated as active pairs, with their rotational axes intersecting at a single point, thereby creating a hemispherical workspace akin to that of a serial mechanism. To implement the active universal pair within a parallel mechanism, we replaced the spherical 5-link mechanism, which originally featured two stationary active rotational pairs, with stationary active universal pairs, and conducted an inverse kinematics analysis. Subsequently, we assessed the expansive workspace of the spherical 5-link mechanism, a key factor influencing the working area of the 3-USR-type 6-DOF parallel mechanism, by examining its motion transmissibility. Based on this evaluation, we designed two compact mechanisms that provide a large workspace and allow for the configuration of all three rotational axes to intersect at a single point. We experimentally investigated the relationship between motion transmissibility and rigidity for these two types of spherical 5-link mechanisms, demonstrating that motion transmissibility can serve as an indicator of rigidity. Finally, a prototype of the 3-USR mechanism was fabricated.

Jerk limited continuous tool path generation for flexible systems in non-cartesian coordinate systems

Inspired by computer numerical control (CNC) technology and drastic changes in the world of electronics and microcontrollers, the idea of using non-cartesian coordinate system for CNC machines became a topic of interest. Non-cartesian coordinate systems provide freedom of movement in systems with large working spaces where high dimensional accuracy is not a prime concern. Applications of such systems can be found in murals, where a painting is applied to a large wall of any arbitrary build material. In the present paper, a new design was introduced to automate the process of drawing murals on large surfaces. The proposed mechanism utilized chain and sprocket to overcome the size limitations of traditionally available x-y tables. In addition to that, the developed mechanism does not utilize the common robust structures used in the conventional CNC systems and the tool motion is created using flexible arms that are not heavily constrained. The effect of systems unwanted vibration has been eliminated using continuous trajectory and kinematic profiles. Parametric curve interpolation algorithms for trajectory planning were implemented to increase the flexibility of drawing complex curves. Parametric curves such as B-spline and non-uniform rational B-spline (NURBS) were employed to generate a jerk limited trajectory for motion control and extraction of kinematic profiles. Such trajectory constrains the jerk of the system and guarantees a smooth motion free of feed-rate fluctuations. Compared to other methods available for extracting the kinematic profiles, jerk limited method decreases the travel time and trajectory error. Ultimately, motion commands were produced by using kinematic profiles and the second order Taylor interpolator. STM32746ZG card was used as the main processor and two stepper motors controlled by a Bit Pattern interpolation algorithm were utilized to drive the proposed mechanism. The input pulses of stepper motors were stored as binary bits and transmitted to drivers in real-time. The feedback was also evaluated by two rotary encoders, placed at the end of the motors’ shafts. Encoder data were acquired and transmitted using a TCP/IP protocol to guarantee zero data loss during the transmission.

Working space planning for wheeled robot overturning stability

Abstract Mobile manipulators have been widely used in the field of building construction. Typical features of construction robots include crossing various rugged terrains in construction sites, carrying heavy payloads, and performing tasks in a large workspace, which may lead to unstable posture or overturning. The tipping of the mobile manipulator, especially when carrying a payload, will cause danger to the surrounding environment and staff, leading to the termination of the task. The purpose of this study is to establish a real-time tipping prediction system, which can be used to avoid tipping of mobile manipulators. By employing the CAD model of the robot and parameters such as the center of gravity and direction, we can ascertain and assess the instability of the robot and the overturning algorithm, thus providing early warning and averting any potential danger.

On-demand robotics—The best of both worlds for robotic-assisted laparoscopic surgery

A modular, combined use of robotic and laparoscopic platforms has been suggested to address challenges in optimal workspace utilization. The 3-arm on-demand open Dexter Robotic System was developed to combine the advantages of robot-assisted precision surgery in narrow spaces with the laparoscopic approach for frequent position changes in larger spaces. The system integrates 2 patient carts, a fully controllable endoscope arm, and a sterile surgeon open console, allowing for a rapid switch between robot-assisted surgery and laparoscopy. When switching, the robotic arms may be folded into a laparoscopic home position at any time during a procedure, allowing unrestricted access to the patient. Switches take 15–30 seconds, occurring seamlessly without redocking or recalibrating upon returning to the robotic mode. During oncologic colorectal resections, some procedure steps (eg, central vessel ligation and lymphadenectomy) are best suited for the robotic approach, providing advantages related to 3-dimensional vision, improved ergonomics, and improved dexterity within confined spaces. In contrast, the laparoscopic platform is better suited for procedure steps requiring frequent movements within a large workspace (eg, lateral to medial mobilization of the colon). The Dexter system provides a portfolio of 7 robotic instruments with monopolar and bipolar function operating with any existing available generator. Furthermore, existing operating room equipment, including insufflating devices, optics, and trocars can be used with the Dexter robotic platform. Recently, the first published clinical experience from the authors’ institution, involving 12 pilot cases, demonstrated the safety and feasibility for right colonic resections for benign and malignant indications and ventral mesh rectopexies.

Modeling magnetic soft continuum robot in nonuniform magnetic fields via energy minimization

The emerging magnetic soft continuum robots (MSCRs) – a type of slender and soft rods with embedded hard-magnetic particles – hold great promise in endovascular intervention via remote magnetic actuation. Although numerous advantages of using permanent magnets have been demonstrated for manipulating MSCRs (e.g., simple systems with high actuation force, large operating workspace), the magneto-mechanical behavior of MSCRs in nonuniform magnetic fields, particularly those generated by permanent magnets, remains largely unexplored. In this work, a systematic study of MSCRs in the nonuniform field is presented, which includes theoretical modeling using hard-magnetic elastica theory, numerical analyses by energy minimization method, finite element simulations using ABAQUS user element (UEL), and experimental validation. Without solving governing differential equations, the large deflection of MSCRs is efficiently obtained via the minimization of the total potential energy using sequential quadratic programming (SQP). This efficient modeling method offers insights into the control of MSCRs using nonuniform magnetic fields. Two practical strategies are provided for precisely controlling MSCRs by manipulating a cubic magnet through the adjustment of the actuation distance, rotation angle, and spin angle, laying the foundation for applications of magnetically-assisted endovascular intervention.

Vision-based autonomous robots calibration for large-size workspace using ArUco map and single camera systems

The low positioning accuracy of industrial robots limits their application in industry. Vision-based kinematic calibration, known for its rapid processing and economic efficiency, is an effective solution to enhance this accuracy. However, most of these methods are constrained by the camera's field of view, limiting their effectiveness in large workspaces. This paper proposes a novel calibration framework composed of monocular vision and computer vision techniques using ArUco markers. Firstly, a robot positioning error model was established by considering the kinematic error based on the Modified Denavit-Hartenberg model. Subsequently, a calibrated camera was used to create an ArUco map as an alternative to traditional single calibration targets. The map was constructed by stitching images of ArUco markers with unique identifiers, and its accuracy was enhanced through closed-loop detection and global optimization that minimizes reprojection errors. Then, initial hand-eye parameters were determined, followed by acquiring the robot's end-effector pose through the ArUco map. The Levenberg-Marquardt algorithm was employed for calibration, involving iterative refinement of hand-eye and kinematic parameters. Finally, experimental validation was conducted on the KUKA kr500 industrial robot, with laser tracker measurements as the reference standard. Compared to the traditional checkerboard method, this new approach not only expands the calibration space but also significantly reduces the robot's absolute positioning error, from 1.359 mm to 0.472 mm.

Improving Robotic Milling Performance through Active Damping of Low-Frequency Structural Modes

Industrial robots are increasingly prevalent due to their large workspace and cost-effectiveness. However, their limited static and dynamic stiffness can lead to issues like mode coupling chatter and regenerative chatter in robotic milling processes, even at shallow cutting depths. These problems significantly impact performance, product quality, tool longevity, and can damage robot components. An active inertial actuator was deployed at the milling spindle to enhance dynamic stiffness and suppress low-frequency vibrations effectively. It was identified that the characteristics of the actuator change with its mounting orientation, a common scenario in robotic machining processes. This variation has not been reported in the literature. Our study includes the identification of model parameters for the actuator in both horizontal and vertical mountings. Additionally, the novelty of the present work lies in the specific design and implementation of compensation filters tailored for the active inertial actuator in both horizontal and vertical configurations. These filters address the unique challenges posed by low-frequency vibrations in robotic milling, offering significant improvements in dynamic stiffness and vibration suppression. Traditional model-based compensators were effective for vertical mounting, while pole-zero placement techniques with minimum phase systems were optimal for horizontal mounting. These compensators significantly enhanced dynamic stiffness, reducing maximum low-frequency robot structural modes by approximately 100% in horizontal mounting and approximately 214% in the vertical configuration of the actuator. This advancement promises to enhance industrial robot capabilities across diverse machining applications.