Amir Firouzeh

Sensor and actuator integrated low-profile robotic origami

The robotic origami (Robogami) is a low-profile, sheet-like robot with multi degrees-of-freedom (DoF) that embeds different functional layers. Due to its planar form, it can take advantage of precise 2D fabrication methods usually reserved for micro and nano systems. Not only can these methods reduce fabrication time and expenses, by offering a high precision, they enable us to integrate actuators, sensors and electronic components into a thin sheet. In this research, we study sensors, actuators and fabrication methods for Robogami which can reconfigure into various forms. Our main objective is to develop technologies that can be easily applied to Robogamis consisting of many active folds and DoFs. In this paper, after studying the performance of the proposed sensors and actuators in one fold, we use a design for a crawler robot consisting of four folds to assess the performance of these technologies.

Soft pneumatic actuator with adjustable stiffness layers for Multi-DoF Actuation

The soft pneumatic actuators (SPAs) are a solution toward the highly customizable and light actuators with the versatility of actuation modes, and an inherent compliance. Such flexibility allows SPAs to be considered as alternative actuators for wearable rehabilitative devices and search and rescue robots. The actuator material and air-chamber design dictate the actuators mechanical performance. Therefore, each actuator design with a single pressure source produces a highly customized motion but only a single degree of freedom (DoF). We present a novel design and fabrication method for a SPA with different modes of actuation using integrated adjustable stiffness layers (ASLs). Unlike the most SPA designs where one independent chamber is needed for each mode of actuation, here we have a single chamber that drives three different modes of actuation by activating different combinations of ASLs. Adapting customized micro heaters and thermistors for modulating the temperature and stiffness of ASLs, we considerably broaden the work space of the SPA actuator. Here, a thorough characterization of the materials and the modeling of the actuator are presented. We propose a design methodology for developing application specific actuators with multi-DoFs that are light and compact.

An under actuated robotic arm with adjustable stiffness shape memory polymer joints

Various robotic applications including surgical instruments, wearable robots and autonomous mobile robots are often constrained with strict design requirements on high degrees of freedom (DoF) and minimal volume and weight. An intuitive design to meet these contradictory requirements is to embed locking mechanism in under actuated robotic manipulators to direct the actuation from a single and remote source to drive different joints on demand. Mechanical clutches do serve such purposes but often are bulky and require auxiliary mechanism making it difficult to justify the high cost adding the additional DoF, especially in cm scale. Here, we introduce an under-actuated robotic arm with shape memory polymer (SMP) joints. Through controlling the temperature, the stiffness of the joints can be adjusted and selected joints will be activated while the rest are fixed in their position. The presented prototype can control the joints independently with a coupled actuation from two stepper motors. Since we have redundant DoFs in the arm, there can be more than one configuration to reach a given position. We use a probabilistic technique to determine the optimum configuration with the minimum number of active joints that can yield the desired posture. In this paper, we report on the performance of the proposed design for the hardware and the configuration planner.

Stiffness Control With Shape Memory Polymer in Underactuated Robotic Origamis

Underactuated systems offer compact design with easy actuation and control but at the cost of limited stable configurations and reduced dexterity compared to the directly driven and fully actuated systems. Here, we propose a compact origami-based design in which we can modulate the material stiffness of the joints and thereby control the stable configurations and the overall stiffness in an underactuated robot. The robotic origami, robogami, design uses multiple functional layers in nominally two-dimensional robots to achieve the desired functionality. To control the stiffness of the structure, we adjust the elastic modulus of a shape memory polymer using an embedded customized stretchable heater. We study the actuation of a robogami finger with three joints and determine its stable configurations and contact forces at different stiffness settings. We monitor the configuration of the finger using feedback from customized curvature sensors embedded in each joint. A scaled down version of the design is used in a two-fingered gripper and different grasp modes are achieved by activating different sets of joints.

The Design and Modeling of a Novel Resistive Stretch Sensor With Tunable Sensitivity

Wearable technologies, interactive and safe robotic systems require an effective actuator control that highly depends on the accurate feedback from flexible and dense array of sensors. In this paper, we introduce a novel soft stretch sensor design that is applicable to distributed high strain measurements. The proposed sensor design utilizes 2-D fabrication processes to create specific profiles and stretchable mesh patterns in Constantan-polyimide laminate that are scalable and customizable. In addition to the geometrical parameters of the stretchable mesh pattern, the sensitivity in the proposed design is determined by the metal layer profile. Without considerably affecting its mechanical properties and stretchability, the profile design allows an engineering freedom to choose the scope of measurements and the sensitivity. Similar design principle can eventually produce complete sensor/circuit systems, where the circuitry and the sensing elements can coexist in a single metal laminate. In this paper, we describe the sensor design parameters and the sensor model that include the equations of deformation and resistance change as a function of the stretch. We compare the prototype test results to the model prediction. The findings provide guideline to designing customized sensors that satisfies specific size and stretch requirements.

A Low Profile Electromagnetic Actuator Design and Model for an Origami Parallel Platform

Thin foldable origami mechanisms allow reconfiguration of complex structures with large volumetric change, versatility, and at low cost; however, there is rarely a systematic way to make them autonomously actuated due to the lack of low profile actuators. Actuation should satisfy the design requirements of wide actuation range, high actuation speed, and backdrivability. This paper presents a novel approach toward fast and controllable folding mechanisms by embedding an electromagnetic actuation system into a nominally flat platform. The design, fabrication, and modeling of the electromagnetic actuation system are reported, and a 1.7 mm-thick single-degree-of-freedom (DoF) foldable parallel structure reaching an elevation of 13mm is used as a proof of concept for the proposed methodology. We also report on the extensive test results that validate the mechanical model in terms of the loaded and unloaded speed, the blocked force, and the range of actuation.

Grasp Mode and Compliance Control of an Underactuated Origami Gripper Using Adjustable Stiffness Joints

Every robotic gripper requires an equilibrated solution towards the grasp adaptability, precision, and load-bearing capacity. A versatile soft robotic gripper requires adjustable grasp mode for objects with different sizes and shapes, and adjustable compliance for switching between soft mode for small loads and delicate objects and stiff mode for larger loads and heavier objects. In this paper, we present the design of a tendon-driven robotic origami, robogami, gripper that provides self-adaptability and inherent softness through its redundant and underactuated degrees of freedom (DoF). Robogami is a planar and foldable robotic platform that is scalable and customizable thanks to its unique layer-by-layer manufacturing process. The nominally two-dimensional fabrication process allows embedding different functional layers with a high fidelity. In particular, a polymer layer with adjustable stiffness enables the independent control of the stiffness for each joint. Using this feature, we can control the input energy distribution between different joints and hence the motion of the robogami. Here, we model the behavior of a single finger, and demonstrate the compliance control of the end effector along different directions in simulations and experiments. We also validate the grippers task versatility in soft and stiff modes by assigning model-based joints stiffness for performing different grasp modes.