Series elastic actuators (SEAs) achieve output torque and stiffness control by managing the deformation of a spring arranged between the motor and the output. SEAs are ideal for tasks involving human-robot interaction and unstructured environments. The stiffness, size, and torque capacity of the spring are crucial for the performance of an SEA. To increase the torque capacity of an SEA while maintaining a compact size, this paper proposes a novel helical flexure as the spring in an SEA. The helical flexure is formed on the thin wall of a tube to generate high torque output with minimal reaction forces and moments. The resulting compliant tube can be combined with other transmission components to reduce the number of components and allow the inner passage of cables and shafts. Simulation comparisons and experimental testing verify the merits of the proposed helical flexure. An SEA prototype is fabricated to demonstrate the performance of the new helical flexure during zero-torque and high-torque motion.

Various sensorized grippers have been developed to handle delicate objects safely. These grippers have sensors mounted on their fingers’ surface that provide direct force measurements. However, multiple sensors are often required on one finger, leading to significant sensor placement and wire routing complexity. Finger-based sensors are limited to sensing external gripping force, and fingers cannot be easily replaced to meet the requirements of objects with specific geometries. To overcome the complexity and limitations of finger surface sensors, this paper proposes a force-controlled two-fingered gripper that relies on the deformation sensing of elastic elements in the drivetrain to obtain finger force. By using a minimum number of optical encoders placed in the drivetrain, accurate position and force sensing can be achieved at any location of each finger. When gripping an object, the size and stiffness of the object can thus be accurately measured. Simulation and experimental results demonstrate the proposed gripper’s merits. We expect this new gripper to provide a more competitive solution for robots that need to manipulate objects and check their mechanical qualities at the same time.

Because of the interest of 3D images and the popularity of World Wide Web, the number of 3D scene/objects and model database throughout the world is growing both in number and in size. VRML (Virtual Reality Modeling Language) is used to model the 3D object of the Web page, and become as a standard for 3D information. Most content-based retrieval (CBR) techniques such as shape and color comparison among objects are for image and video. The mechanisms are designed based on 2D information. In this paper, we propose a new similarity method, based on 3D information extracted from a VRML object database. The system includes multiple subsystems, which are conducted in two main parts. The first part includes the VRML object parser system and the normalization system. The second part includes the comparison system, database management system and a friendly graphical user interface. The method is the first step of our project, which aims to incorporate feature extraction of virtual reality objects, such as chairs, car, and others in 3D space. House interior designers can use the proposed system. The user can select proper scenes and furniture in order to meet the requirement of potential customers.

Building a web-based distributed multimedia presentation system environment is a technical challenge .In this paper, we described how to present different multimedia objects on a web presentation system with floor control mechanism as a result of the distributed environment indispensably. The distributed approach is based on an extended timed Petri net model. Using characterization of extended time Petri net, we introduce the concepts of user interaction. The main goal of our system is to provide a feasible method to represent different multimedia objects with user interaction and floor control mode. In addition, users can dynamically request different kinds of conditions during the presentation. To verify the structural mechanism, we implement an algorithm using the Extend Time Petri net model. Futhremore, we consider the interactive facilities to support the distributed communication requirement. We specified a floor control algorithm based on Z notation, which provides four types of control (free access, equal control, group discussion, and direct contact). These control mechanisms are sufficient to the use of distance learning environment.