Robotic manipulators are highly nonlinear and coupled systems that are subject to different types of disturbances such as joint frictions, unknown payloads, varying contact points, and unmodeled dynamics. These disturbances, when unaccounted for, adversely affect the performance of the manipulator. Employing a disturbance observer is a common method to reject such disturbances. In addition to disturbance rejection, disturbance observers can be used in force control applications. Recently, research has been done regarding the design of nonlinear disturbance observers (NLDOs) for robotic manipulators. In spite of good results in terms of disturbance tracking, the previously designed nonlinear disturbance observers can merely be used for planar serial manipulators with revolute joints (Chen, W.H., Ballance, D.J., Gawthorp, P.J., O'Reilly, J., 2000. A nonlinear disturbance observer for robotic manipulators. IEEE Trans. Ind. Electron. 47, 932-938), (Nikoobin, A., Haghighi, R., 2009. Lyapunov-based nonlinear disturbance observer for serial n-link manipulators. J. Intell. Robot. Syst. 55,[135][136][137][138][139][140][141][142][143][144][145][146][147][148][149][150][151][152][153]. In this paper, a general systematic approach is proposed to solve the disturbance observer design problem for robotic manipulators without restrictions on the number of degrees-of-freedom (DOFs), the types of joints, or the manipulator configuration. Moreover, this design method does not need the exact dynamic model of the serial robotic manipulator. This method also * Corresponding author, Tel.: +1 (647) unifies the previously proposed linear and nonlinear disturbance observers in a general framework. Simulations are presented for a 4-DOF SCARA manipulator to show the effectiveness of the proposed disturbance observer design method. Experimental results using a PHANToM Omni haptic device further illustrate the effectiveness of the design method.

Herein, how robotic and autonomous systems and smart wearables complement and support healthcare delivery and the healthcare staff during the COVID‐19 pandemic are presented. For instance, robotic and telerobotic systems significantly reduce the risk of infectious disease transmission to frontline healthcare workers by making it possible to triage, evaluate, monitor, and treat patients from a safe distance. Various examples of where the medical, engineering, and science communities come together to aid the healthcare system, healthcare workers, and society during the current crisis are presented. The goal is to encourage an interdisciplinary dialog so that ethical, practical, and beneficial technological solutions are found to effectively tackle this and similar crises.

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Measurements of the attenuation and velocity of ultrasound from 0.3 to 0.8 MHz have been performed on a number of bovine cancellous bone samples. The influence of bone mineral content has been isolated by measuring the acoustic properties of the samples at various stages of demineralization resulting from controlled nitric acid attack. The correlation coefficient r, between the attenuation at different frequencies and bone density was found to be in the range 0.68-0.97. Broadband ultrasonic attenuation (BUA) was also calculated and produced r values between 0.84 and 0.99. The velocity measurements indicated a correlation greater than 0.97 in all cases. Thus velocity is the parameter most sensitive to changes in bone mineral density alone. Attenuation and BUA are less well correlated presumably because of a sensitivity to minor structural change.

In master-slave teleoperation applications that deal with a delicate and sensitive environment, it is important to provide haptic feedback of slave/environment interactions to the user's hand as it improves task performance and teleoperation transparency (fidelity), which is the extent of telepresence of the remote environment available to the user through the master-slave system. For haptic teleoperation, in addition to a haptics-capable master interface, often one or more force sensors are also used, which warrant new bilateral control architectures while increasing the cost and the complexity of the teleoperation system. In this paper, we investigate the added benefits of using force sensors that measure hand/master and slave/environment interactions and of utilizing local feedback loops on the teleoperation transparency. We compare the two-channel and the four-channel bilateral control systems in terms of stability and transparency, and study the stability and performance robustness of the four-channel method against nonidealities that arise during bilateral control implementation, which include master-slave communication latency and changes in the environment dynamics. The next issue addressed in the paper deals with the case where the master interface is not haptics capable, but the slave is equipped with a force sensor. In the context of robotics-assisted soft-tissue surgical applications, we explore through human factors experiments whether slave/environment force measurements can be of any help with regard to improving task performance. The last problem we study is whether slave/environment force information, with and without haptic capability in the master interface, can help improve outcomes under degraded visual conditions.

Conventional endoscopic surgery has some drawbacks that can be addressed by using robots. The robotic systems used for surgery are still in their infancy. A major deficiency is the lack of haptic feedback to the surgeon. In this paper, the benefits of haptic feedback in robot-assisted surgery are discussed. A novel robotic end-effector is then described that meets the requirements of endoscopic surgery and is sensorized for force/ torque feedback. The endoscopic end-effector is capable of non-invasively measuring its interaction with tissue in all the degrees of freedom available during endoscopic manipulation. It is also capable of remotely actuating a tip and measuring its interaction with the environment without using any sensors on the jaws. The sensorized end-effector can be used as the last arm of a surgical robot to incorporate haptic feedback and/or to evaluate skills and learning curves of residents and surgeons in endoscopic surgery.

The measurement of attenuation and velocity of ultrasound in cancellous bovine femora has been studied. The dependence of both attenuation between 0.2 and 0.8 MHZ and velocity on the bone density has been measured. The results show a correlation coefficient of around 0.5 for attenuation and density, and a value of roughly 0.85 for velocity and density. The clinical consequences for the use of low frequency ultrasound as a diagnostic tool in bone disease are discussed.

For robotic systems that use on/off (solenoid) pneumatic actuators, a sliding mode control law for precise position control and low switching (open-close) activity of the valves is presented in this paper. Given a pneumatic actuator with two chambers and four solenoid valves, there are sixteen possible input combinations defined directly from the state of the four on/off valves present in the system; however, only seven of these discrete operating modes are considered both functional and unique. Therefore, we introduce a novel seven-mode sliding controller that minimizes the position tracking error using modes that have both the necessary and sufficient amounts of drive energy and, thus, involve reduced switching activity. An analysis of the closed-loop system stability is carried out. The performance of the proposed control design is experimentally verified on a single pneumatic actuator setup comprising of two chambers with four on/off valves.