Chen Qiu

• Doctor of Philosophy
• Research Associate at Nanyang Technological University

This book addresses the design of compliant mechanisms, presenting readers with a good understanding of both the solid mechanics of flexible elements and their configuration design, based on a mechanism-equivalent approach in the framework of screw theory. The book begins with the theoretical background of screw theory, and systematically addresses...

Compliant grasping is an essential capability for most robots in practical applications. For compliant robotic end-effectors that commonly appear in industrial or logistic scenarios, such as Fin-Ray gripper, it still remains challenging to build a bidirectional mathematical model that mutually maps the shape deformation and contact force. Part I of...

Compliant grippers, owing to adaptivity and safety, have attracted considerable attention for unstructured grasping in real applications, such as industrial or logistic scenarios. However, accurate construction of the mathematical model depicting the bidirectional relationship between shape deformation and contact force for such grippers, such as t...

Soft robotic grippers have attracted considerable attention in terms of the advantages of the high compliance and robustness to variance in object geometry; however, they are still limited by the corresponding sensing capabilities. We propose a novel soft gripper that looks like a ‘granary’ in the geometrical shape with a snap-through bistable mech...

We propose a parallel massage robot with compliant joints based on the series elastic actuator (SEA), offering a unified force-position control approach. First, the kinematic and static force models are established for obtaining the corresponding control variables. Then, a novel force-position control strategy is proposed to separately control the...

A massage robot can aid physicians in treating occupational diseases. While massaging, a robotic manipulator is required to continuously exert desired force according to the predefined motion pattern on a body surface. The complexity of the mechanical and control system, high cost, and heavy structure of the existing massage robots result in the li...

This paper provides a geometrical insight into the dualities of compliant mechanisms via repelling screws. A method for the construction of the repelling screw system is proposed. By means of screw theory and linear algebra, the closed-loop relationships among the twist/wrench spaces of both actuation- and constraint-screw systems are identified, u...

Grasping is an essential capability for most robots in practical applications. Soft robotic grippers are considered as a critical part of robotic grasping and have attracted considerable attention in terms of the advantages of the high compliance and robustness to variance in object geometry; however, they are still limited by the corresponding sen...

This chapter presents the conceptual design of compliant mechanisms. The fundamental idea behind it is to establish the relationship between freedom and constraint space of a compliant mechanism according to the reciprocal relationship between twists and wrenches. By using the constraint-based design approach, a flexible element can be represented...

Further the large deformation problem of compliant mechanisms is investigated in this chapter. As has been discussed in Sect. 4.4.4, when a compliant mechanism is under a large external load, the corresponding stiffness matrix is no longer symmetric and invariant. However, its force equilibrium still holds the same and it is used here to explore th...

This book presented a comprehensive study of screw theory and its application in the design of compliant mechanisms. In the framework of screw theory, both the design of flexible elements as well as their integration were appropriately addressed. This led to the further exploration of both theoretical and practical design problems of compliant mech...

In this chapter, screw theory is introduced as a preliminary study to give readers an overview of screw theory and its application in compliant mechanism designs. The definition of a screw, as well as the key screw operations, are given in Sect. 2.2, such as the interchange operation of a screw, the screw coordinate transformation and the reciproca...

After developing the compliance/stiffness matrix of a compliant mechanism, the next step is to evaluate the performance of the compliant mechanism based on the developed compliance/stiffness matrix. Sometimes this requires either an explicit or implicit expressions of compliance/stiffness matrix with respect to design parameters of the compliant me...

Following the design of flexible elements in Chap. 3, their integration is further discussed in this section, which eventually leads to the construction of compliant mechanisms. The typical integration type of flexible elements includes serial, parallel and hybrid. Since the hybrid configuration is always a mixture of the first two types, this chap...

Following the conceptual design of compliant mechanisms in Chap. 5, this chapter further looks into the stiffness properties of the developed compliant parallel mechanisms. Two types of stiffness problems are investigated, including the stiffness analysis and synthesis problem. In the stiffness analysis, the reciprocal relationship between motions...

As discussed in Sect. 2.4, the definitions of the twist and wrench describe the instantaneous velocity (infinitesimal displacement) of a rigid body and the external load applied at it in the framework of screw theory. Also, an example is given to demonstrate their application in describing the degrees of freedom and constraints of a compliant paral...

Performing a grasp is a pivotal capability for a robotic gripper. We propose a new evaluation approach of grasping stability via constructing a model of grasping stiffness based on the theory of contact mechanics. First, the mathematical models are built to explore "soft contact" and the general grasp stiffness between a finger and an object. Next,...

Performing a grasp is a pivotal capability for a robotic gripper. We propose a new evaluation approach of grasping stability via constructing a model of grasping stiffness based on the theory of contact mechanics. First, the mathematical models are built to explore soft contact and the general grasp stiffness between a finger and an object. Next, t...

The stability is of utmost important for achieving a reliable fingertip grasp. In this work, we focus on building the model of optimization design of the fingertip to evaluate the best fingertip shape and determining the size range of objects grasped by fingertips steadily. We describe the effect of fingertip dimension on the stability of fingertip...

Abstract The design optimization of a robotic gripper is of utmost importance for achieving a stable grasp behaviour. This work focuses on analysing the optimal design of an under-actuated tendon-driven robotic gripper with two 3-phalange fingers and a geometric design optimization method is proposed to achieve a stable grasp performance. The probl...

This paper presents a co-rotational concept for large-deflection formulation of cardiac catheters. Using this approach, the catheter is first discretized with a number of equal length beam elements and nodes, and the rigid body motions of an individual beam element are separated from its deformations. Therefore, it is adequate for modelling arbitra...

Automated ultrasound scanning is a growing research field. However, existing platforms for mounting the ultrasound probe do not possess any soft, compliant properties that would ensure the safety of the patient. Moreover, many current ultrasound manipulators do not include tactile feedback or employ rather expensive commercial force sensors. This p...

There is a surge of research interest in the field of “continuum robotics.” Robots created under this paradigm offer many advantages and represent unique features in terms of flexibility, dexterity, safety, and weight reduction. This paper introduces a novel continuum manipulator that integrates multiple layers of compliant planar springs—a structu...

This paper investigates the ortho-planar spring's six-dimensional compliance characteristics using a compliance matrix based approach, and validate them with both finite element simulations and experiments. The compliance matrix is developed by treating an ortho-planar spring as a parallel mechanism, which is revealed to be diagonal for the first t...

This paper presents a novel design of extensible continuum robots in light of origami-inspired folding techniques. The design starts from a modularized crease pattern, which consists of two triangular bases and three waterbomb bases, and generates a folding process for creating an origami waterbomb parallel structure. This further progresses to gen...

This paper provides an approach to model the reaction force of origami mechanisms when they are deformed. In this approach, an origami structure is taken as an equivalent redundantly-actuated mechanism, making it possible to apply the forward-force analysis to calculating the reaction force of the origami structure. Theoretical background is provid...

In order to obtain more truly finite element model to reflect the dynamic and static mechanical properties of offshore derricks, a finite element model updating method of derrick structures is proposed combined with dynamic and static objective functions. Compared with the single use of static or dynamic objective function in model updating, it can...

This paper investigates both stiffness analysis and synthesis problems using a physical prototype of one SPS orthogonal parallel mechanism. This parallel mechanism is supported with line-type constraint limbs. In the stiffness analysis, a reciprocal relationship between motions and wrenches is used to design layouts of constraint limbs and construc...

This paper presents a novel design for continuum robots in light of origami inspired folding techniques. The work of the present paper starts from design of a crease pattern, which consists of two triangular bases and three waterbomb bases, and folding process for creating an origami parallel structure in 3D from the crease pattern in 2D. Mapping t...

This paper provides a systematic approach to design a vehicle’s independent suspension system. In this approach, multi-link type suspension is selected. By treating it as a parallel mechanism, both the kinematic design and force analysis are conducted in the same framework of screw theory. Regarding the kinematic design, constraint-based approach i...

The wormlike robots are capable of imitating amazing locomotion of slim creatures. This paper presents a novel centimeter-scale worm robot inspired by a kirigami parallel structure with helical motion. The motion characteristics of the kirigami structure are unravelled by analyzing the equivalent kinematic model in terms of screw theory. This revea...

This paper introduces a novel continuum-style robot that integrates multiple layers of compliant modules. Its essential features lie in that its bending is not based on natural compliance of a continuous backbone element or soft skeletal elements but instead is based on the compliance of each structured planar module. This structure provides severa...

Ortho-planar spring is a compact spring that generates the motion based on the deformation of flexure elements, and it has wide applications in the compliant robotic designs. Previous studies only investigate the out-of-plane compliance of ortho-planar spring and fewer work pays attention to its angular compliance. To address this issue, this paper...

This paper presents a novel compliant parallel mechanism that utilizes shape-memory-alloy (SMA) spring based actuators. By employing SMA coil springs, the traditional line constraint that resists translation along its axis but no other forms of motions is transformed into a linear actuator that can generate deflection along its axis, which leads to...

Origami-type cartons have been widely used in packaging industry because of their versatility, but there is a lack of systematic approach to study their folding behavior, which is a key issue in designing packaging machines in packaging industry. This paper addresses the fundamental issue by taking the geometric design and material property into co...

In this study, we present an analytical approach for synthesizing line actuation spaces of a parallel flexure mechanism (PFM) that can help designers to arrange linear actuators within the PFM in a correct and optimal way. On the basis of screw theory and upon an assumption of small deformations, an important synthesis criterion stated as “any actu...

This paper investigates the stiffness characteristics of an origami-type carton, which can be modeled into an equivalent mechanism by considering creases as revolute joints and panels as links. Stiffness characteristics of a single crease is investigated regarding its relationships with folding angular velocity and crease length. Based on the kinem...

This paper introduces an approach for synthesis of actuation spaces of multi-axis parallel flexure mechanisms. The concept of actuation space, first proposed by J. Hopkins and M. Culpepper, is developed from constraint and freedom space, which are two fundamental concepts in constraint-based method. Within the framework of screw theory, actuation a...