Regulatory network for FOREVER YOUNG FLOWER-like genes in regulating Arabidopsis flower senescence and abscission.

FOREVER YOUNG FLOWER (FYF) has been reported to play an important role in regulating flower senescence/abscission. Here, we functionally analyzed five Arabidopsis FYF-like genes, two in the FYF subgroup (FYL1/AGL71 and FYL2/AGL72) and three in the SOC1 subgroup (SOC1/AGL20, AGL19, and AGL14/XAL2), and showed their involvement in the regulation of flower senescence and/or abscission. We demonstrated that in FYF subgroup, FYF has both functions in suppressing flower senescence and abscission, FYL1 only suppresses flower abscission and FYL2 has been converted as an activator to promote flower senescence. In SOC1 subgroup, AGL19/AGL14/SOC1 have only one function in suppressing flower senescence. We also found that FYF-like proteins can form heterotetrameric complexes with different combinations of A/E functional proteins (such as AGL6 and SEP1) and AGL15/18-like proteins to perform their functions. These findings greatly expand the current knowledge behind the multifunctional evolution of FYF-like genes and uncover their regulatory network in plants.

Optimal Design of a Compliant Constant-Force Mechanism to Deliver a Nearly Constant Output Force Over a Range of Input Displacements.

This study presents an optimal design procedure, including topology and geometry optimization methods to design a compliant constant-force mechanism, which can generate a nearly constant output force over a range of input displacements. The proposed constant-force mechanism is a passive force regulation device that can be used in various applications such as precision manipulation and overload protection. The numerical optimization problem is treated as an error minimization problem between output and objective forces. Both material and geometric nonlinearities are considered in topology and geometry optimization steps. Although the element stiffness for void and gray elements after topology optimization are quite small comparing with solid elements, their existence also contributes to the output force characteristic of the synthesized mechanisms. As these low-stiffness elements are not easy to manufacture in physical prototype, a helical compression spring is introduced in the topology optimized constant-force mechanism to account for the effect of low-stiffness elements, and an additional geometry optimization step is utilized to identify the spring constant as well as to fine-tune the geometric parameters. The optimized constant-force mechanism is prototyped by three-dimensional printing using flexible thermoplastic elastomer. The experimental results show that the proposed design can generate a nearly constant output force in the input displacement range of 3-6 mm. The developed constant-force mechanism is installed on an electric gripper drive mounted on a robot arm for robotic picking and placing application. Test results show the constant-force gripper can be used in handling of size-varied fragile objects.

Optimal Design of a Soft Robotic Gripper for Grasping Unknown Objects.

This study presents the design of an underactuated, two-finger, motor-driven compliant gripper for grasping size-varied unknown objects. The gripper module consists of one main frame structure and two identical compliant fingers. The compliant finger is a monolithic compliant mechanism synthesized using a topology optimization method, and then prototyped by 3D printing using flexible filament. The input port for each finger is mounted on a moving platform driven by a gear motor, whereas the fixed port of the finger is mounted on a fixed platform. Each compliant finger can be actuated through the linear motion of the moving platform, and can deform elastically to generate the grasping motion. To demonstrate the effectiveness of the proposed design, the gripper module is mounted on a six-axis robotic arm to pick and place a variety of objects. The results show that objects with the sizes between 42 and 141 mm can be grasped by the developed soft robotic gripper. The maximum payload for the gripper is 2.1 kg. The proposed compliant gripper is a low-cost design that can be used in grasping of size-varied vulnerable objects.