Design and Characterization of a Low-Cost and Efficient Torsional Spring for ES-RSEA

The design of torsional springs for series elastic actuators (SEAs) is challenging, especially when balancing good stiffness characteristics and efficient torque robustness. This study focuses on the design of a lightweight, low-cost, and compact torsional spring for use in the energy storage-rotary series elastic actuator (ES-RSEA) of a lumbar support exoskeleton. The exoskeleton is used as an assistive device to prevent lower back injuries. The torsion spring was designed following design for manufacturability (DFM) principles, focusing on minimal space and weight. The design process involved determining the potential topology and optimizing the selected topology parameters through the finite element method (FEM) to reduce equivalent stress. The prototype was made using a waterjet cutting process with a low-cost material (AISI-4140-alloy) and tested using a custom-made test rig. The results showed that the torsion spring had a linear torque-displacement relationship with 99% linearity, and the deviation between FEM simulation and experimental measurements was less than 2%. The torsion spring has a maximum torque capacity of 45.7 Nm and a 440 Nm/rad stiffness. The proposed torsion spring is a promising option for lumbar support exoskeletons and similar applications requiring low stiffness, low weight-to-torque ratio, and cost-effectiveness

Postural comfort of driver works space in vehicle package design geometry: A pilot study on malaysian drivers in sedan car and MPV

The study of driver posture and comfort in driver workspace is important in vehicle package design especially in two different type of vehicle, sedan and Multi-Purpose Vehicle (MPV). Due to different seat position in the driver workspace, investigation of driver accommodation in relations to driver anthropometry is essential to ensure its meet the ergonomic quality. Therefore, this research is to investigate the preferred driving posture of Malaysian driver in both sedan and MPV type of car. Sixty two subjects (32 males and 30 females) aged between 17-60 years old were selected to simulate the comfortable driving posture using mock-ups of sedan car and MPV. Measurements based on SAE J1100 vehicle package design geometry were carried out for each subject. Result shows slight differences in the range of posture angle between the two types of vehicles, the posture joint angle in MPV is slightly smaller as compared to those of sedan car. The range postural angles for Malaysian driver population also is slightly smaller compare to Caucasian people especially on lower body portion such as knee angle, hip angle and ankle angle. These angles are due to the body stature and body segment length in which the population of Malaysia have shorter thighs and legs than those in Europe and America

Design for environment and design for disassembly practices in Malaysia: a practitioner's perspectives

Design for Environment (DIE) and Design for Disassembly (DID) have been recognized as an effective sustainable manufacturing approach to reduce environmental impact during product's life cycle. Although Malaysian manufacturers have long demonstrated a strong global market presence, the implementation of DIE and DID among manufacturers are found lacking. This paper attempts to investigate the current state DIE and DID implementation and the local driving force in the local Malaysian industry by addressing four research questions (RQ): RQ1 - How do Malaysian designers value the importance of DIE? RQ2 - What are the current approaches used by designers to incorporate environmental issues during product development stage? RQ3 - What difficulties are experienced in the implementation of DIE and DID in the product development stage? RQ4 - What are the approaches needed to enhance the engagement of DIE and DID into product design practices? Targeting product designers in Malaysia, a multiple approach using survey and interview is conducted shown that the current state of implementation and awareness within the local industry is fairly low. The soft approach of the local legislation does not contribute much towards seeing a major change in attitude as will be discussed further in the paper. The above two concerns are major challenges that require immediate attention. However, there seems to be growing concern from the industry and the government that pushes the need for options that could leapfrog the current situation. This presents an opportunity for the local research community to come up with various strategies that will be discussed. Finally, the paper proposes a more comprehensive strategy that is tailored to the local business environment in order for the local industry to be capable of maintaining its market presence. (C) 2015 Elsevier Ltd. All rights reserved

Insert geometry effects on surface roughness in turning process of AISI D2 steel

Surface roughness is an important parameter for ensuring that the dimension of geometry is within the permitted tolerance. The ideal surface roughness is determined by the feed rate and the geometry of the tool. However, several uncontrollable factors including work material factors, tool angle, and machine tool vibration, may also influence surface roughness. The objective of this study was to compare the measured surface roughness (from experiment) to the theoretical surface roughness (from theoretical calculation) and to investigate the surface roughness resulting from two types of insert, `C' type and `T' type. The experiment was focused on the turning process, using a lathe machine Colchester 6000. The feed rate was varied within the recommended feed rate range. We found that there were large deviations between the measured and theoretical surface roughness at a low feed rate (0.05 mm/r) from the application of both inserts. A work material factor of AISI D2 steel that affects the chip character is presumably responsible for this phenomenon. Interestingly, at a high feed rate (0.4 mm/r), the `C' type insert resulted in 40% lower roughness compared to the `T' type due to the difference in insert geometry. This study shows that the geometry of an insert may result in a different surface quality at a particular level of feed rate