Design of the Wearable Spatial Gravity Balance Mechanism

Gravity compensation mechanisms are widely used in manipulators and exoskeletons as passive components which generate counter-gravity force and save energy. While there have been making great progresses in the design of the planar gravity compensator and its spatial counterpart, a strict condition that the axes of the gravity compensators are aligned with the axes of the links being balanced (LBBs) exactly is usually assumed implicitly. In this paper, the design method of the wearable spatial gravity compensator compatible to the misalignment and drift of the rotation center of the LBB is carefully studied. First, the design of the planar gravity compensation unit (PGCU) is presented, and then it is adapted into the spatial gravity compensation unit (SGCU) by the motion features of the fixed-point rotation. Then, the type synthesis of the SGCU is conducted followed by the analyses of the acting patterns of synthesized SGCUs on the LBBs and gravity compensation performances when the misalignments and drifts of rotation centers of the LBBs occur. Finally, the SGCUs can be combined with timing belt mechanisms (TBMs) to construct gravity compensation mechanisms for spatial serial linkages. Simulations of the exoskeleton constructed by SGCUs are conducted to verify the performance of gravity balance and the effectiveness of the proposed design method.

Bioinspired Divide-and-Conquer Design Methodology for a Multifunctional Contour of a Curved Lever

In this study, we propose a bioinspired design methodology for a multifunctional lever based on the morphological principle of the lever mechanism in the Salvia pratensis flower. The proposed divide-and-conquer contour design methodology does not treat a lever contour as a single curve that satisfies multiple functions. Rather, the lever contour combines partial contours to achieve its assigned subfunction. This approach can simplify the complex multifunctional problem in lever design. We include a case study of a lever utilized in a compact variable gravity compensator (CVGC) to explain the methodology in more detail. In the case study, four partial contours were designed to satisfy three types of functional requirements. The final design for the lever contour was manufactured and verified with visual measurement experiments. The experimental result shows that each partial contour successfully achieved its subfunctions.

Industrial Exoskeletons With Gravity Compensation Elements

The chapter approaches the issues of modeling the process of load lifting by a person while wearing an exoskeleton. The classification of existing gravitational compensation systems for industrial exoskeletons is shown, as well as examples of its use. A mathematical model of lifting a person's load in the exoskeleton is presented, as well as numerical parameters are calculated. It is shown that the introduction of an elastic element reduces the level of energy consumption during work, and can also facilitate the level of the worker. Industrial exoskeleton prototype design is presented. A particular focus is given to studying the influence of the gravity compensator on the magnitude of the moments generated by the electric drives of the hip and knee joints. It is shown that the use of gravity compensators enables to reduce significantly the load on electric drives.

Simulation of an Exoskeleton with a Hybrid Linear Gravity Compensator

Purpose of research. Development of a mathematical model of an exoskeleton equipped with a hybrid linear gravity compensator (HLGC), dynamic analysis on the example of a typical exoskeleton application scenario (in the process of lifting a load), obtaining time patterns of changes in system parameters, including electric drive torques allowing assessment of power plan power consumption and energy efficiency. The article deals with the challenging issue of improving the efficiency of the exoskeletal suit by means of HLGC. The use of a hybrid approach makes it possible to increase the efficiency of assisting the exoskeletal suit when performing various technological operations, for example, when lifting a load, when tilting and holding. Methods. When developing a mathematical model, an original approach was used to form the motion trajectory of the exoskeleton sectors during operation, based on the use of seventh-order polynomials. The paper uses a mathematical model represented by a system of second-order differential equations that connects the moments acting on the operator and the exoskeleton, the angular accelerations of the operator's back and the exoskeleton. Results. During numerical simulation, time diagrams of changes in system parameters, angles of rotation of exoskeleton hinges, moments that occur in a hybrid LGC, as well as graphs of current consumption of engines when performing lift and tilt with a load are obtained. Conclusion. In the course of the research, a kinematic model of an exoskeleton suit equipped with a GLGC was developed, second-order differential equations describing the dynamic behavior of the electromechanical system were written, and numerical simulation was performed to estimate the forces and energy consumption in the exoskeleton hinges and the drive of the hybrid linear gravity compensator.