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.

Perancangan Dan Pembuatan Mesin 3D Printer Tipe Cantilever

Teknologi 3D printing termasuk dalam metode manufaktu rbaru yang disebut dengan metode additive manufacturing. Metode ini mempunyai cara kerja menumpuk material untuk membuat sebuah objek 3 dimensi. Penelitian dalam bidang desain dan assembly mesin 3D printer masih belum banya kdilakukan. Pada umumnya, mesin-mesin 3D printer yang digunakan memiliki paling tidak 5 motor stepper, yaitu sumbu X 1 buah, sumbu Y 1 buah, sumbu Z 2 buah serta motor ekstruder 1 buah. Paper ini akan membahas mengenai alternative desain mesin 3D printer FFF dengan model cantilever yang menggunakan 4 motor stepper sehingga lebih hemat komponen. Proses desain dan assembly 3D printer tipe cantilever menghasilkan mesin dengan area kerja 200 x 200 x 200 mm dan ketelitian 0,1 mm. Mesin 3D printer yang didesain memiliki komponen utama berupa komponen mekanik dan elektrik. Komponen mekanik terdiri dari frame, linear guide, bracket, leadscrew, pulley dan timing belt. Komponen elektrik terdiri dari controller, lcd, motor stepper, limit switch, soket serta power supply. Dengan meminimalisir jumlah motor stepper yang digunakan, maka desain 3D printer tipe cantilever dinilai lebih ekonomis dengan desain yang minimalis. Mesin seperti ini cocok digunakan untuk kegiatan-kegiatan yang bersifat mobile. 3D printer ini kedepan akan dimanfaatkan untuk melakukan pelatihan kepada masyarakat untuk memperkenalkan teknologi manufaktur baru, yaitu proses cetak 3 dimensi.

Investigation on the Rotational Dynamics of a Timing Belt Drive Including an Oval Driving Pulley

Recent developments in timing belt drive for the automotive engine have seen the use of non-circular pulleys. This study presents an experimental and numerical investigation on this type of transmission including an oval pulley. A specific test rig has been designed to enable the identification of the proper effect of an oval pulley on the transmission dynamics. The belt tensions, the speeds, and torques of the driving and driven pulleys were measured and analyzed for three different transmission configurations: (1) circular driving pulley and oval driving pulley without (2) and/or with (3) load torque applied. Analyses were carried out in the time and frequency domains by considering the driving pulley rotation angle as a reference. In parallel a numerical model has been developed, it accounts for the specific motions of the belt seating/unseating points on the oval pulley and its neighboring pulleys. The model considers the variation of lengths for the belt spans adjacent to the oval pulley. This induces variable longitudinal stiffness and influences the transmission dynamics that is predicted versus time and compared with experiments. The phasing angle of the oval driving pulley was adjustable in order to study its influence. With no resistant torque applied, it was found that, for low-speeds, the oval pulley has a pure kinematic effect on the transmission dynamics. When a load torque is applied, the effectiveness of the oval pulley regarding the belt tensions and transmission error fluctuations is verified experimentally for some specific intervals of the phasing angle.

Determining the Power Consumption of the Automatic Device for Belt Perforation Based on the Dynamic Model

The subject of the dynamic analysis presented in the article is the linear drive system with a timing belt utilized in the automatic device for polymer composite belt perforation. The analysis was carried out in two stages. In the first stage, the timing belt was modeled with all the relevant dynamic phenomena; subsequently, the tension force of the belt required for the correct operation of the belt transmission was determined. The necessary parameters for belt elasticity, vibration damping, and inertia are based exclusively on the catalog data provided by the manufacturer. During the second stage, equations of motion were derived for the designed drive system with a timing belt, and characteristics were identified to facilitate the optimal selection of electromechanical drives for the construction solution under analysis. The presented methodology allows for designing an effective solution that may be adapted for other constructions. The obtained results showed the influence of the kinematic parameters on the motor torque and proved the importance of reducing the mass of the components in machines that perform high-speed processes.

An approach for the quantitative description of uncertainty to support robust design in sensing technology

Sensing machine elements offer the potential to upgrade conventional machine elements by extending their primary function to be able to measure a quantity of interest at its point of origin in a technical system, the so-called in situ measurement. To ensure the functionality of these next generation machine elements, special attention must be paid to uncertainty in terms of modelling to be able to correctly evaluate the provided signal and obtain reliable information. Consequently, this contribution describes an approach to classify uncertainty in sensing technology, especially in SMEs, based on the amount of available information, which can be used as a point of departure to reduce the impact of occurring uncertainty to improve the robustness of the obtained signal. Starting from the understanding of uncertainty and the corresponding classification scheme as well as its linkage to robust design from the Collaborative Research Centre 805, a quantitative model is presented to determine the impact of uncertainty on a measuring signal. The applicability of the proposed approach is demonstrated using the example of a sensing timing belt by taking into account the uncertainty from the SME itself and also from the surrounding technical system.