Carsten Schürmann

Flexible and stretchable fabric-based tactile sensor

We introduce a novel, fabric-based, flexible, and stretchable tactile sensor, which is capable of seamlessly covering natural shapes. As humans and robots have curved body parts that move with respect to each other, the practical usage of traditional rigid tactile sensor arrays is limited. Rather, a flexible tactile skin is required. Our design allows for several tactile cells to be embedded in a single sensor patch. It can have an arbitrary perimeter and can cover free-form surfaces. In this article we discuss the construction of the sensor and evaluate its performance. Our flexible tactile sensor remains operational on top of soft padding such as a gel cushion, enabling the construction of a human-like soft tactile skin. The sensor allows pressure measurements to be read from a subtle less than 1?kPa up to high pressures of more than 500?kPa, which easily covers the common range for everyday human manual interactions. Due to a layered construction, the sensor is very robust and can withstand normal forces multiple magnitudes higher than what could be achieved by a human without sustaining damage.As an exciting application for the sensor, we describe the construction of a wearable tactile dataglove with 54 tactile cells and embedded data acquisition electronics. We also discuss the necessary implementation details to maintain long term sensor performance in the presence of moisture. A flexible and stretchable durable fabric-based tactile sensor capable of capturing typical human interaction forces was developed.We present elaborate measurement results of the sensor.A process of creating multiple sensor areas in a single fabric patch was developed.The measures against performance degradation due to moisture are presented.Using the developed technology, a tactile dataglove with 54 pressure sensitive regions was built.

A control framework for tactile servoing

The advent of sensor arrays providing tactile feedback with high spatial and temporal resolution asks for new control strategies to exploit this important and valuable sensory channel for grasping and manipulation tasks. In this paper, we introduce a control framework to realize a whole set of tactile servoing tasks, i.e. control tasks that intend to realize a specific tactile interaction pattern. This includes such simple tasks like tracking a touched object, maintaining both contact location and contact force, as well as more elaborate tasks like tracking an object’s pose or tactile object exploration. Exploiting methods known from image processing, we introduce robust feature extraction methods to estimate the 2D contact position, the contact force, and the orientation of an object edge being in contact to the sensor. The flexible control framework allows us to adapt the PID-type controller to a large range of different tasks by specification of a projection matrix toggling certain control components on and off. We demonstrate and evaluate the capabilities of the proposed control framework in a series of experiments employing a 16×16 tactile sensor array attached to a Kuka LWR as a large fingertip.

A modular high-speed tactile sensor for human manipulation research

Tactile sensing is an important field of research in the domains of human-computer and human-robot interaction. To provide appropriate tactile sensing capabilities, this work presents the development of a new modular tactile sensor system focusing especially on high frame rates (up to 1.9 kHz) and good spatial resolution (5 mm). Larger sensor areas are composed from identical sensor modules providing a 16×16 matrix of tactels. We compare different tactel layouts and different force-sensitive materials to achieve optimal sensitivity especially to low forces in order to facilitate detection of first touch. An example application demonstrates the capability of the developed sensor to detect tiny variations in applied force.

A highly sensitive 3D-shaped tactile sensor

In this paper we introduce a novel way of producing highly sensitive 3D-shaped tactile sensors. The sense of touch is critical for enabling humans to master intricate manual interactions. Numerous anthropomorphic robots make extensive use of complex three dimensional body parts in mimicry of their biological counterparts. We use laser structuring technology to augment freeform surfaces with conductive tracks, paving the way for the manufacturing of 3D-shaped tactile sensors. The signal acquisition electronics can be effortlessly embedded on the backside of an artificial layer of skin. We evaluate the performance of the sensor and discuss the results in detail. As an exciting application, we produced a tactile fingertip sensor for the Shadow Robot Hand that incorporates 12 tactile sensor regions and the embedded signal acquisition electronics. The integrated microcontroller is able to capture force patterns with a frame-rate of more than 1 kHz, allowing object slippage to be detected.

Tactile dataglove with fabric-based sensors

This paper introduces a novel, fabric-based, flexible, and stretchable tactile sensor, capable of seamlessly covering natural shapes. Our design allows for several tactile cells to be embedded in a single sensor patch, and can have an arbitrary perimeter and can cover freeform surfaces. The sensor remains operational on top of soft padding, facilitating the possibility to build human-like artificial skin. It provides force measurements from subtle to high forces (0.1-30N), which easily covers the common range for everyday human manual interactions. Due to a layered construction, the sensor is very robust and can withstand huge normal forces without sustaining damage. We discuss the construction of the sensor and evaluate its performance. As an exciting application for the sensor, we describe the construction of a wearable tactile dataglove with 54 tactile cells.

A High-Speed Tactile Sensor for Slip Detection

Dexterous grasping and manipulation of objects with robot hands requires the ability to monitor contact locations in real-time and with good spatial resolution in order to close the control loop required for object and contact trajectory generation. The ability to recognize incipient slippage will allow for autonomous grasp force adaption – a major prerequisite to handle objects of unknown weight.

Analysis of human grasping under task anticipation using a tactile book

Motivated by the prominent role of haptics for the analysis of human grasping and manipulation and the replication of similar abilities for humanoid robots, we developed a device capable to augment conventional motion capture techniques with the real-time acquisition of high-resolution spatio-temporal pressure patterns between hand and manipulated object. The device is the shape and size of a book, covered with a grid of small-sized (5 mm diameter) sensors and processing electronics to provide a stream of “tactile images” at 180 Hz frame per second. Additionally integrated acceleration sensors allow to correlate the tactile image stream with accurate motion information. We discuss design considerations, implementation and data processing and illustrate the capabilities of the device with an experiment studying grasping strategies during a pick-and-place task and the impact of different end-states on the recorded grasping patterns.