Huan Zhao

• Doctor of Engineering
• Professor at Huazhong University of Science and Technology

Direct visual servoing considers all pixel intensities of the entire image as inputs for robot control. Because of the high dimensionality of the image space, it achieves high convergence accuracy at the cost of low convergence domain. Recent work on the direct visual servoing decomposes the images into different signal spaces. Although a large con...

Micro-grinding has been widely used in aerospace and other industry, and its application was mainly the asymmetric microstructure. Chemical Vapor Deposition (CVD) diamond has drawn attention for its good wear resistance. However, the small diameter and high spindle speed may cause difficulties on the monitoring of the micro-grinding processes. In o...

This paper addresses the machining requirements for large aerospace structural components using robotic systems and proposes a method for rapid workpiece positioning that combines the simplicity of vision-based positioning with the precision of contact-based methods. To enhance the accuracy of robot calibration, a novel approach utilizing a ruby pr...

Novice surgeons perform incompetently during robotic surgical teleoperation because of poor consistency, a laparoscopic view that lacks depth information, and low proficiency. To make the novice surgeon perform close to expert operation during teleoperation, this article proposes an auxiliary framework for robotic surgery. A Bayesian statistics-bas...

Accurate anatomical landmark tracking is crucial yet challenging in laparoscopic surgery due to the changing appearance of landmarks during dynamic tool-anatomy interactions and visual domain shifts between cases. Unlike appearance-based detection methods, this work proposes a novel graph-based approach to reconstruct the entire target landmark are...

Surgical procedures are inherently complex and dynamic, with intricate dependencies and various execution paths. Accurate identification of the intentions behind critical actions, referred to as Primary Intentions (PIs), is crucial to understanding and planning the procedure. This paper presents a novel framework that advances PI recognition in ins...

The original K-means algorithm is widely applied for clustering in Euclidean spaces. Nevertheless, due to the non-flat characteristics of the Riemannian manifold, standard Euclidean K-means algorithms yield inferior results on such data. To address this issue, this paper presents an intrinsic K-means clustering algorithm on homogeneous manifolds ba...

Carbon fiber reinforced thermoplastic (CFRTP) composites, known for their excellent mechanical properties and environmental sustainability, are highly sought‐after in aerospace, energy, and many other fields. Grinding could be used to realize the high‐accuracy and low‐damage machining of CFRTP components. However, due to the temperature sensitivity...

Grinding could be used to enhance accuracy and quality of carbon fiber‐reinforced poly‐ether‐ether‐ketone (CF/PEEK) composites. However, the grinding mode, namely up‐grinding (UG) or down‐grinding (DG), is usually neglected while unbefitting grinding mode choice may cause inferior surface quality. To investigate effects of grinding modes on grindin...

Minimally invasive endovascular interventional surgery has become the primary surgical method for treating cardiovascular and cerebrovascular diseases. Robotic technology has been proposed as a means to enhance surgical procedures and improve physician experience. Despite the development of related technologies and the proposal of many robotic endo...

Soft tool grinding is promising as a flexible machining method known for its remarkable advantages, such as expansive contact areas, deformation-based compliance to curved surfaces, and effective vibration absorption, thereby ensuring heightened efficiency and superior surface quality. Nevertheless, attaining precise part contours necessitates an a...

To distinguish the grinding performance of the multidirectional (MD) and unidirectional (UD) carbon fiber‐reinforced thermoplastic (CFRTP) composites, MD and UD carbon fiber‐reinforced poly‐etherether‐ketone (CF/PEEK) composites were employed in this study. Different ply stacking sequences and process parameters were set for grinding experiments. S...

Chatter is a serious problem in grinding, which will directly affect machining accuracy, efficiency, tool wear and even damage machine tools. In order to understand and avoid grinding chatter, a stability prediction and optimization method of multi-regenerative weak stiffness grinding system based on microstructured tool is innovatively proposed. I...

Due to the large state–action space and statically indeterminate problem, it is difficult to analyze the robotic multiple peg-in-hole (PIH) assembly tasks, which results in a scarcity of effective and general multiple PIH assembly strategies and control methods. This is particularly evident when faced with situations involving a large number of peg...

Electrical connectors (ECs) are extensively employed in industrial scenarios, and their assembly quality is crucial. However, these connectors are often located in confined spaces, which poses challenges of complex lighting conditions and visual occlusions during the execution of robotic assembly tasks. Hence, guiding robots to assemble solely thro...

Accurate assessment of guidewire shape and contact forces is critical for autonomous robotic endovascular procedures. However, existing sensor-based approaches often require modifications to standard guidewires or the use of custom-made alternatives, which can hinder integration into conventional surgical workflows and increase costs. Moreover, the...

This paper addresses the robot machining requirements for large aerospace structural components and provides a method for rapid workpiece positioning in robot machining systems that combines the ease of visual measurement-based positioning with the precision of contact-based positioning. In order to enhance the precision of the robot calibration sy...

The typical industrial robots, though highly repeatable, have relatively low path accuracy. As the main source of the path deviations, joint flexibility-induced position errors between motor and link called joint position errors (JPEs) are difficult to compensate directly in the robot controller due to the lack of link-side encoders for most indust...

The remote perception of teleoperated surgical robotics has been a critical issue for surgeons in fulfilling their remote manipulation tasks. In this article, an adaptive teleoperation control framework is proposed. It provides a physical human–robot interaction interface to enhance the ability of the operator to intuitively perceive the material p...

Surgical workflow analysis integrates perception, comprehension, and prediction of the surgical workflow, which helps real-time surgical support systems provide proper guidance and assistance for surgeons. This paper promotes the idea of critical actions , which refer to the essential surgical actions that progress towards the fulfillment of the...

Dual mobile manipulators are increasingly used in cooperative operation tasks, and their appropriate joint configurations are the premise to ensure the success of the tasks. However, for a given task path, due to the existence of redundant degrees of freedom, there are countless possible joint configurations, which makes it difficult to solve the i...

In order to distinguish the grinding performance of the thermoset and thermoplastic carbon fiber‐reinforced plastic (CFRP) composites, carbon fiber‐reinforced epoxy resin (CF/epoxy) and carbon fiber‐reinforced poly‐ether‐ether‐ketone (CF/PEEK) composites were employed in this study. Different process parameters were set to grind the two materials....

Owing to the increased complexity of contact state, compared with the problem of robotic single peg-in-hole assembly, little research and few efficient solutions are currently available for the robotic multiple peg-in-hole assembly, particularly when the number of peg-hole pairs exceeds three. For this reason, a novel robotic multiple peg-in-hole a...

Calibrating unknown transformation relationships is an essential task for multirobot cooperative systems. Traditional linear methods are inadequate to decouple and simultaneously solve the unknown matrices due to their intercoupling. This article proposes a novel dual-robot accurate calibration method that uses convex optimization and Lie derivativ...

Due to their high flexibility, large workspace, and high repeatability, industrial robots are widely used in roughing and semifinishing fields. However, their low machining accuracy and low stability limit further development of industrial robots in the machining field, with low stiffness being the most significant factor. The stiffness of industri...

Complex surfaces are widely used in aerospace, energy, and national defense industries. As one of the major means of manufacturing such as complex surfaces, the multi-axis numerical control (NC) machining technique makes much contribution. When the size of complex surfaces is large or the machining space is narrow, the multi-axis NC machining may n...

The automated laparoscope control can ensure the stability of the laparoscopic image and enhance the performance of surgeons during surgical operations. The letter presented a method that autonomously adjusted the laparoscope pose to obtain the optimal field of view (FOV). An optimization problem was constructed to generate the laparoscope pose, wh...

The K-means algorithm is widely applied for clustering, and its clustering effect is influenced by its initialization. However, most existing works focus on the initialization of K and centers in Euclidean spaces, but few works in the literature deal with the initialization of K-means clustering on Riemannian manifolds. In this paper, we propose a...

Purpose Branched articulated robots (BARs) are highly non-linear systems; accurate dynamic identification is critical for model-based control in high-speed and heavy-load applications. However, due to some dynamic parameters being redundant, dynamic models are singular, which increases the calculation amount and reduces the robustness of identifica...

In order to investigate the material removal mechanism of carbon fiber-reinforced thermoplastics (CFRTP), nanoscratching experiments of carbon fiber-reinforced polyetheretherketone (CF/PEEK), as a typical kind of thermoplastic composite, were performed along various feed directions of the indenter and fiber orientations. Material removal mechanism...

Curved parts in the industry have characteristics of large curvature variance and small error allowance, which makes it difficult to control material removal accuracy during the compliant grinding process. Existing studies mainly focused on controlling material removal accuracy by using constant contact force or pressure strategies, while there is...

Closed-chain robots have great advantages in machining complex components, especially under high-speed and heavy-load conditions. Accurate dynamic model is fundamental importance to obtain good performance. However, most existing works focus on the excitation trajectories and identification methods, but few works of literature deal with the accurac...

Robots are increasingly employed in machining applications, such as milling, grinding and polishing, etc, and contour error can be used to assess the robotic machining accuracy quantitatively. For the robotic machining tasks, such as the grinding of complex surface parts, the reduction of contour error needs to consider the six dimensions of the ro...

Robot manipulators with 6 degree-of-freedom (DOF) have advantages of good flexibility and large working space. However, the relatively low stiffness deteriorates the machining accuracy and stability in robotic milling tasks, which restricts the widely application of robotic milling in industry. To increase the machining accuracy, taking advantage o...

When using robots to carry out grinding and polishing processing of industrial blades, due to factors such as non-zero approach speed and discontinuous dynamic characteristics, the robot grinding and polishing processing has contact force impact and oscillation problems during the contact transition process, which seriously affects the quality of t...

Industrial robots are characterized by good flexibility and a large working space, and offer a new approach for the machining of large and complex parts with small machining allowances (extra material allowed for subsequent machining). Parts of this type (such as aircraft skin parts, wind turbine blades, etc.) are easily deformed due to their large...

Due to the robustness to robot modeling and camera calibration errors and avoidance of complete target geometry, image-based visual servoing has always been an important topic in the fields such as robotics, computer vision and so forth. When the image information obtained by the camera is mapped to the robotic task space to design the servoing con...

Compared with CNC machines, articulated robots show significant pose-dependent dynamic characteristics. Thus, the chatter mechanism of robot milling is murky. Furthermore, trajectory accuracy is also dependent on robot pose, resulting in complexity of the robot milling stability. In this paper, robot trajectory tracking error, independent from tool...

Regenerative chatter, a kind of undesirable self-excited vibration, has been widely found in the milling of flexible parts due to the weak rigidity, which imposes a major limitation on workpiece quality and processing efficiency. To achieve the goal of high-performance machining, online chatter detection attracts the attention of many researchers....

The iterative pre-compensation method can predict the optimal pre-compensation value and compensate the tracking error effectively, but the compensation effect decreases if parameters of drive systems change. This paper proposes a variable-parameter-model-based iterative pre-compensation method of the tracking error, which can predict the optimal p...

Because of the low cost, large workspace and high flexibility, industrial robots (IRs) are promising and competitive alternatives of multi-axis machine tools for milling operations. However, the deformation induced by the low posture-dependent stiffness of robot significantly deteriorates the contour accuracy of milling. Existing studies mainly foc...

Peg-in-hole assembly with narrow clearance is a typical robotic contact-rich task in industrial manufacturing. Robot learning allows robots to directly acquire the assembly skills for this task without modeling and recognizing the complex contact states. However, learning such skills is still challenging for robot because of the difficulties in col...

Impedance control is an effective force tracking approach for robotic contact operation tasks such as grinding/polishing, deburring, assembly and dexterous hand manipulations, etc. Within the impedance control framework, when the robot begins to contact with the environment, however, force oscillations may occur even if the optimal approach velocit...

Three-dimensional feature descriptors play an important role in 3D computer vision because they are widely employed in many 3D perception applications to extract point correspondences between two point clouds. However, most existing description methods suffer from either weak robustness, low descriptiveness, or costly computation. Thus, a 3D local...

The manufacturing sector is envisioned to be heavily influenced by artificial-intelligence-based technologies with the extraordinary increases in computational power and data volumes. A central challenge in the manufacturing sector lies in the requirement of a general framework to ensure satisfied diagnosis and monitoring performances in different...

With no force sensors, estimating forces for robotic manipulation has gained a lot of attention. However, for industrial robots with harmonic drives (flexible joints), deviations between joint and motor positions inevitably deteriorate the force estimation performance due to the lack of encoders on the joint side. To this end, this paper presents a...

Aiming at solving the robotic grinding problem of aircraft engine blades with complex surface, this paper proposed an adaptive force control method using fuzzy PID algorithm, which can ensure that blade surface is completely polished to eliminate residual texture and harmful stress concentration. First, an intelligent digital compliant grinder with...

Recently, because of better flexibility and lower cost than CNC machine tools, industrial robots have been widely used in the manufacturing of complex surface parts, especially in blade grinding. However, studies on robotic blade grinding path planning are relatively less and it is still a challenge to realize path planning under constant force con...

Aircraft-engine blade has a free-form surface in space, which is extremely complicated. And the surface milling must be polished completely to eliminate the surface residual texture and stress concentration. To solve this problem, an intelligent digital compliant grinder with active and passive compliance, double-end floating and multi-station poli...

The final finishing technology of wind turbine blade is usually manual polishing and robotic polishing is a very meaningful but still hard task. This paper presents a novel strategy by combining a force control polishing device and contact force control algorithm. Specifically, the polishing device is electrically driven, which has advantage of hig...

Component-based contouring error control is a typical contouring control method for five-axis CNC machine tools. However, the existing studies based on this method still have two problems: (1) the contouring errors may increase in some regions rather than a reduction; (2) the reduction of contouring errors in other regions is limited. In this paper...

Polishing of thin-walled blisks can easily lead to vibrations and affect the surface quality. To solve this problem, we present a novel smart end effector for active contact force control and vibration suppression in robotic polishing of thin-walled blisks. A gravity-compensated force controller is developed to maintain the contact force between th...

Within the impedance control framework, an adaptive scheme was developed to generate the reference trajectory and improve the force tracking performance by using an iterative learning algorithm. First, an adaptive scheme was used to estimate the environment stiffness and location such that an accurate reference trajectory could be obtained. Subsequ...

This paper presents a novel two degrees of freedom (DOFs) contact force control method for robotic blisk grinding. The grinding tool is controlled to automatically adapt to the curvity change of the blisk blade and maintain a constant contact force as expected. A smart end effector is used as the actuating device for contact force control. The prop...

The machining accuracy of five-axis CNC machine tools is usually measured by contour error. The traditional contour error reduction strategies mainly include accurate contour error estimation and effective contouring controller design. However, there are problems in traditional strategies, such as online contour error estimation or complex controll...

Nowadays, the tool path in five-axis machining is usually described with linear segments. Tangential and curvature discontinuities of the linear tool path lead to poor machining efficiency and quality. Due to the complexities in constraining approximation errors and synchronization of tool tip position and tool orientation, it still remains a chall...

Robotic machining is an increasing application due to various advantages of robots such as flexibility, maneuverability and competitive cost. For robotic machining, the machining accuracy is the major concern of current researches. And particular attention is paid to the proper modeling of manipulator stiffness properties, the cutting force estimat...

The milling robot normally has a low stiffness which may easily cause chatter during machining. This article presents a novel eddy current damper design for chatter suppression in the robotic milling process. The designed eddy current dampers are installed on the milling spindle to damp the tool tip vibrations. The structural design and the working...

Without the 3-D geometry of the target and robust to camera calibration error, image-based visual servoing schemes have gained a lot of attention. However, the depth of the selected feature, which is involved in the interaction matrix relating the time variation of the feature to the velocity twist of the camera, must be estimated correctly to guar...

For free form surfaces such as blades, their measurement accuracy and efficiency depend on the planning strategy of discrete sampling points and the compensation precision of probe tip error. However, the force information is not considered in the traditional adaptive sampling and error compensation methods, which may affect the measurement efficie...

High accuracy contour error estimation and direct contour error control are two major approaches to reduce the contour error. However, two key factors make them complex for five-axis machine tools: the nonlinear kinematics and the coupling between the tool position and orientation. In this study, by finding the reference point nearest to the curren...

Multi-axis motion systems have been widely applied in industrial fields, and the contour error is an important indicator to measure the quality of the products. Contour error is defined as the orthogonal deviation of actual position from the desired tool path, and contouring control is a very useful method to reduce or eliminate it. In this study,...

Collision avoidance is the major concern for the multi-robots operation. However, few literatures can generate a collision free path as well as a smooth motion profile at the same time. To solve this problem, this paper presents an integrated motion planning scheme for two manipulators working in a shared workspace. In this method, first, a collisi...

In the robotic belt grinding process, the parameters such as robot feedrate and contact force play important roles on the material removal. In order to minimize the machining time and achieve high accuracy, a scheduling method of trajectory and force is proposed to maximize the robot feedrate. First, an optimization model with the constraints of jo...