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Improving the capabilities of online condition monitoring systems, able to detect arising of catastrophic wear on cutting tools, has been an important target to be pursued for the metal cutting industry. Currently, different systems have been proposed, moved by the rising need of part quality improvements and production cost control. Despite this, cutter wear development, being related to several process variables and conditions, is still really difficult to be predicted accurately. This paper presents a detection wear method based on the time-domain analysis of vibro-acoustic signals. Specifically, cutter wear monitoring, using sound signals of a milling process, was performed at a laboratory level in a well-isolated working room. Sound signals were recorded at fixed main machining parameters, i.e., cutting speed, feed rate and depth of cut. The tests were carried out starting with a new set of inserts with significant wear conditions for the investigated process configuration. Results showed a consistent overlapping between the beginning of the catastrophic wear and an evident increment in the trend of the root mean square of the monitored acoustic signal, showing the potential of the methodology in detecting a suitable time to stop the milling process and to change the worn-out cutters. [ABSTRACT FROM AUTHOR]

Brain injuries resulting from spinal cord injuries, strokes, or cerebral palsy are among the traumas most capable of compromising the motor activities of human limbs, hence the necessity for the development of exoskeletons dedicated to the rehabilitation of these organs. This review examines the landscape of actuators essential for the design of cutting-edge upper-limb rehabilitation exoskeletal structures. Beyond merely surveying the current types of actuators available, the paper aims to provide guidelines for selecting actuators that fit optimally with the objectives of upper-limb rehabilitation. The description starts with a brief discussion on the biomechanics of the upper limbs, focusing on the kinematics of pivotal joints (wrist, elbow, shoulder). Subsequently, the existing actuators are systematically reviewed, offering detailed insights into their primary features, operational principles, strengths, weaknesses, and noteworthy applications within the realm of rehabilitation robotics. After the discussion about the actuators, the paper advances by furnishing valuable guidelines for actuators' selection tailored for upper limb rehabilitation. These guidelines discuss crucial factors, such as the forces required and the natural Range Of Motions (ROMs) of upper limb joints. Finally, the manuscript serves as a valuable resource for researchers, engineers, and practitioners involved in the development of innovative upper-limb rehabilitation devices. [ABSTRACT FROM AUTHOR]

All machining processes involve vibrations generated by structural sources such as a machine's moving parts or by the interaction between cutting tools and work-pieces. Relative vibrations between the work-pieces and the cutting tool are the most relevant from the point of view of the regenerative chatter phenomenon. In fact, these vibrations can lead to a chip yregeneration effect, which results in unwanted consequences, rapidly degenerating towards a very poor quality of surface finishing or, in case of severe chatter conditions, to machine-tool or work-piece damage. In the past decades, two different approaches for chatter avoidance were proposed by the scientific community, and they are commonly referred to as Out-of-Process (OuP) and in-Process (iP) solutions. The OuP solutions are off-line approaches, which allow to properly set the working parameters before machining starts. Ip solutions are on-line techniques, which allow to dynamically change the working parameters during machining by using single or multiple sensors. By monitoring the machining process, iP algorithms try to keep the machining process in stable working conditions while keeping high productivity levels. This study dealt with a novel iP chatter-detection strategy based on the Power Spectral Density (PSD) analysis and on the Wavelet Packet Decomposition (WPD) of different sensor signals. The preliminary results demonstrate the stability and feasibility of proposed indicators for chatter detection in industrial application. [ABSTRACT FROM AUTHOR]