Soft grippers have shown promising performance in safe and adaptive grasping tasks. However, they often suffer from limitations in grasping force. To address this challenge, this paper presents a novel pneumatic three-finger soft gripper to achieve robust adaptive grasping. The gripper consists of three identical fingers, each containing a pneumatic bending soft actuator and a pneumatic lateral soft actuator. The bending actuator features a tilted pneumatic network structure, which provides superior bending performance compared to traditional vertical pneumatic network structure. The lateral actuator is equipped with three deflection chambers at the finger root to mimic the lateral motions of a human finger. Kinematic and static models are established to predict the bending angle and grasping force of the soft finger under pressurized air. The performance of the proposed soft finger is analyzed through finite element simulations, and the effect of the chamber tilt angle is also examined. The theoretical and simulation results are compared to verify the validity of the analytical models. Finally, the proposed soft gripper is fabricated by 3D printing and molding. Experimental results show that the gripper is capable of grasping various objects of different sizes, shapes, materials, and weights, and can perform dexterous manipulation tasks, such as cap unscrewing. The proposed soft gripper exhibits significant potential for applications in robotic robust grasping tasks.

In this paper, a novel adjustable-stiffness force sensor is developed for multitask measurements requiring different force resolutions and ranges. The applied force of the force sensor is indirectly measured through the linear deformation instead of the structure strain through an optical linear encoder. The main structure of the force sensor is actually a linear variable stiffness mechanism with a compact size and a large stiffness change. Its stiffness can be continuously adjusted by changing the effective second moment of area of the structure. Thus, the force sensor has an adjustable range and resolution since the displacement resolution of the optical linear encoder is constant. The stiffness modeling of the sensor is performed based on the matrix method, which is then evaluated by the finite element analysis. A principle prototype is finally fabricated for the adjustable-stiffness test and a concrete application example. The testing results show that the stiffness and resolution of the force sensor can be changed by the proposed stiffness adjustment. Moreover, it is effective to measure different-resolution forces. This adjustable-stiffness approach can be also extended to the design of a torque sensor or a force/torque sensor.

Parallel surface contact between the template and the substrate is very important in imprint lithography. In this paper, a novel force-decoupled compound parallel alignment stage is proposed for high-resolution imprint lithography. It mainly consists of a high-stiffness spherical air bearing (SAB) and a multi-degree-of-freedom (multi-DOF) flexure-based mechanism that functions for both the active and passive alignments. Apart from the function of the parallel alignment, the proposed stage can also endure a large imprinting force of more than 1000 N but does not cause any damage to the delicate components, which is mainly attributed to its force-decoupled characteristic. Through the stiffness modeling and finite element analysis (FEA), the performance is evaluated to satisfy the design requirement. Finally, experimental tests are conducted on the parallel alignment stage for the hot embossing process, and the grating patterns with linewidth of 2.5 μm are successfully transferred from the silicon template to the polymethy methacrylate (PMMA) substrate. This result demonstrates that the proposed stage can be used in the hot embossing process without degrading its alignment accuracy.

An orthogonal frequency division multiplexing system suffers performance degradation when the length of the cyclic prefix is less than the channel impulse response. The root cause of this degradation is the inter-carrier interference (ICI) and inter-symbol interference (ISI) introduced by the excessive multipath delay. Generally, multiple-input multiple-output (MIMO) beamforming is helpful in mitigating such interference because it can spatially suppress some of the multipath. However, the effectiveness of this suppression is very limited. In this paper, we propose an ICI/ISI-aware beamforming algorithm which explicitly takes into account the multipath characteristic of the channel. Optimal steering vectors are derived to maximize the signal-to-interference-plus-noise ratio. This technique not only achieves the beamforming benefit, but also significantly mitigates the ICI and ISI. We show, via simulations, that the proposed algorithm can dramatically reduce the block error rate, permitting good performance for channel delay profiles that would break conventional links. This is vitally important for the extension of indoor wireless LAN designs to outdoor uses.