The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
This paper proposes a non-dimensional representation for hydraulic arms whose original representation is complex in terms of the nonlinear dynamics and many physical parameters. Unlike the usual nondimensional representations, the proposed nondimensional representation preserves a parametric structure in the original representation. Without loss of generality, only by changing the damping constant,...
Compliant actuator is widely accepted for physical human-robot interaction due to its safety aspect, dynamic performance improvements and energy saving abilities. In this paper, based on the variable ratio lever mechanism, a new kind of Serial Variable Stiffness Actuator (SVSA) is proposed by using an Archimedean Spiral Relocation Mechanism (ASRM) to change the position of the pivot, implementing...
We propose a novel hydraulic hybrid servo drive for robotic applications. This method embeds a small servo-controlled pump into a hydraulic metering circuit. The circuit is compactly integrated into a servo-unit, then replicated for each joint, and connected to one common low-pressure line. Thanks to the boosting effect, one can simultaneously achieve high-load and high-precision servo control performance...
This paper presents a new variable stiffness actuator (VSA) based on a structure-controlled method: controlling the mechanical structure of the actuator by rotating four flexure hinges. The VSA possesses a property that the output position and stiffness are independently controlled. This is realized by a serial arrangement of a principle driving motor, a small stiffness variation motor and a novel...
There has been consistent trials to make a hydraulic actuator to be effective in interactive robot applications that require high power and durability. However, conventional strategies to obtain this goal, such as force/torque servo control or adding elastic components, suffer from complexity, sensor problems, and reduced system robustness. In this paper, we show that introducing backdrivability to...
Classical rigid-bodied robotic systems are presented with proven success in theoretical development and industrial applications, are recently challenged by the emergence of soft robotics due to a growing need in physical human-robot interactions (pHRI), such as wearable devices, medical robots, personal robots, etc. In this paper, we present the design and fabrication of a robust, hybrid bending actuator...
Fluidic actuators allow versatile, agile, and powerful motions and are commonly applied in robotics and automation. Likewise, many biological systems use fluidic actuators implemented with tissue for a wealth of tasks and performances. Spiders for example apply a hybrid mechanism of hydraulically actuated joint extension and muscle-based joint flexion to produce movement in two of their seven leg...
A position-based proportional-derivative (PD) controller with inner torque feedback loops can be used as a simple controller to render compliant behaviors to hydraulic robots. However, using this control framework involves a tradeoff between the stability and performance of the closed-loop system (which includes the external environment) because the joint position sensors and control units (i.e.,...
This paper considers the problem of safe mission planning of dynamic systems operating under uncertain environments. Much of the prior work on achieving robust and safe control requires solving second-order cone programs (SOCP). Unfortunately, existing general purpose SOCP methods are often infeasible for real-time robotic tasks due to high memory and computational requirements imposed by existing...
Hamilton-Jacobi (HJ) reachability is a method that provides rigorous analyses of the safety properties of dynamical systems. These guarantees can be provided by the computation of a backward reachable set (BRS), which represents the set of states from which the system may be driven into violating safety properties despite the system's best effort to remain safe. Unfortunately, the complexity of the...
In this paper, we present an efficient Dynamic Programing framework for optimal planning and control of legged robots. First we formulate this problem as an optimal control problem for switched systems. Then we propose a multi-level optimization approach to find the optimal switching times and the optimal continuous control inputs. Through this scheme, the decomposed optimization can potentially be...
A significant challenge for unmanned aerial vehicles capable of flying long distances is planning in a wind field. Although there has been a plethora of work on the individual topics of planning long routes, smooth trajectory optimization and planning in a wind field, it is difficult for these methods to scale to solve the combined problem. In this paper, we address the problem of planning long, dynamically...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.