In this paper, a modified robust dynamic control (MRDC) method is proposed for a 2-DOF Diamond parallel robot to realize high-precision and high-speed cooperating motion. Diamond robot is a double-input and double-output system with both coupled dynamics and uncertain dynamics. Based on the dynamic equation in joint coordinates, a MRDC that can drive the two active arms of Diamond robot to stay in two decoupled terminal sliding modes with continuous control signals is designed. The control law of MRDC is specially constructed to be insensitive to the noise in speed signal, which can help to improve error convergence speed without causing undesirable system chattering. With suitable control parameters, the proposed MRDC can assure the stability of Diamond robot even in the presence of disturbance, parameter variation, etc., which is verified in sense of Lyapunov. MRDC is then successfully implemented on a Diamond robot prototype controlled by a commercial PMAC motion control card. Experimental results show that proposed MRDC can achieve both good trajectory tracking performance and good robustness against disturbance. Compared with the robust dynamic control and PD control, MRDC can avoid undesirable system chattering and assure better trajectory tracking accuracy respectively.

Soft actuators have received extensive attention in robotics and smart device applications due to their distinctive dexterity and compliance. Among them, hydraulic soft actuators play an important role in the area because they have much higher specific power and power density than other types such as pneumatic soft actuators. Nevertheless, the deformation of flexible materials in soft actuators brings about inherent hysteresis and nonlinearity, which severely hinders them from producing the desired movement in the presence of advanced control strategies. In this paper, previous research efforts made to enhance the driving capability and actuation efficiency of hydraulic soft actuators are illustrated and analyzed from the three aspects of architecture, materials, and control strategy. Meanwhile, the issues and challenges that have emerged when developing hydraulic soft actuators are discussed. Finally, the potential future development of hydraulic powered soft actuators is discussed.

The machine tool equipped with the dual-drive servo feed system could realize high feed speed as well as sharp precision. Currently, there is no report about the thermal behaviors of the dual-drive machine, and the current research of the thermal characteristics of machines mainly focuses on steady simulation. To explore the influence of thermal characterizations on the precision of a jib boring machine assembled dual-drive feed system, the thermal equilibrium tests and the research on thermal-mechanical transient behaviors are carried out. A laser interferometer, infrared thermography and a temperature-displacement acquisition system are applied to measure the temperature distribution and thermal deformation at different feed speeds. Subsequently, the finite element method (FEM) is used to analyze the transient thermal behaviors of the boring machine. The complex boundary conditions, such as heat sources and convective heat transfer coefficient, are calculated. Finally, transient variances in temperatures and deformations are compared with the measured values, and the errors between the measurement and the simulation of the temperature and the thermal error are 2 °C and 2.5 μm, respectively. The researching results demonstrate that the FEM model can predict the thermal error and temperature distribution very well under specified operating condition. Moreover, the uneven temperature gradient is due to the asynchronous dual-drive structure that results in thermal deformation. Additionally, the positioning accuracy decreases as the measured point became further away from the motor, and the thermal error and equilibrium period both increase with feed speeds. The research proposes a systematical method to measure and simulate the boring machine transient thermal behaviors.