Optics: measuring and testing – Position or displacement
Reexamination Certificate
2001-01-05
2003-02-18
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Position or displacement
C073S551000, C073S610000
Reexamination Certificate
active
06522415
ABSTRACT:
The invention is directed to the determination of a relative position of two objects with respect to one another.
A robot is being increasingly employed for assembly work due to electronic and electro-technical progress. This robot is equipped with a flexible gripper system that is in the position of implementing the greatest variety of handling and manipulation tasks.
Document [1] provides an overview of technical systems that are utilized for grasping and manipulating an object. Further, [1] discloses that the grasped object must be in a permanently prescribed position relative to the gripper system, namely such that a prescribable force can be exerted on the object.
It is known from [1] that manipulation means that the position of the grasped object and, potentially, its orientation in space is modified in a predetermined way.
In conjunction with a gripper system, it thereby turns out that the determination of the relative position of the grasped object with respect to the gripper and the force exerted on the grasped object are of particular significance.
It is also known from [1] that what is referred to as an object and contact sensor is employed for determining the position and the force.
What is understood by an object sensor is a sensor that acquires the position of an object. With such a sensor, the position of an object is determined, a known object is recognized and identified and an unknown object is measured.
A typical implementation of this sensor is an ultrasound distance sensor, a laser distance sensor or a camera viewing system.
What is understood by a contact sensor is a sensor that enables a statement about the contact of the gripper with an object. The quantities that can be measured at the contact surface between gripper and object can thereby be subdivided into qualitative and quantitative information. For example, spatial forces and moments as well as the attack point of the force can be qualitatively acquired. Further contact quantities such as gripping and holding forces can be determined from these quantities. The sensor employed for the acquisition of these quantities is also referred to a force sensor.
In contrast thereto, what is referred to as a tactile sensor frequently measures a purely qualitative quantity. An important qualitative information is comprised, for example, therein whether a gripper jaw of a two-jaw gripper as disclosed in [1] has contact with an object. This is often difficult to decide with exclusive employment of a force sensor given a lightweight object. The nature of the contact is another important qualitative information. A further aim is to identify the shape and surface quality of the grasped object with a tactile sensor. Further, the slipping of an object can be determined with a tactile sensor. Further, an object can be recognized, distinguished and a statement about the position and the attitude of the grasped object can be made with the tactile sensor.
Frequently employed embodiments of a contact sensor are a wire strain gauge, a piezoceramic or a semiconductor pressure sensor.
It is also known from [2] that the object sensor and the contact sensor exhibit various disadvantages. Thus, the laser distance sensor and the camera viewing system is [sic] expensive and makes [sic] high demands of an evaluation electronics. In contrast thereto, the ultrasound distance sensor in fact exhibits a low price and a great ruggedness. However, the precision of such a sensor, its susceptibility to disturbance with respect to a temperature fluctuation, an external signal or a multiple reflection and the low range of the sensor make the use thereof only conditionally possible.
Another disadvantage of the known sensors is comprised therein that a plurality of sensors are needed for the simultaneous measurement of a quantitative and qualitative state quantity. This in turn leads thereto that the structural size of such a combined sensor is larger compared to an individual sensor.
The invention is thus based on the problem of determining the relative position of two objects with respect to one another in a simple, flexible and cost-beneficial way as well as with the possibility of a miniaturization of the system.
The problem is solved by the arrangement according to patent claim
1
, the set with a plurality of arrangements according to patent claim
16
as well as by the method according to patent claim
21
.
The arrangement for determining a relative position of two objects with respect to one another comprises a radiation source that is configured such that it generates radiation having a characteristic radiation field. The arrangement further comprises a receiver that is configured for the reception of the radiation, and an evaluation unit coupled to the receiver with which the relative position of the objects with respect to one another can be determined from the signals received from the receiver, said signals being dependent on the reception location in the characteristic radiation field.
The following is to be understood as the characteristic radiation field of the radiation source:
The radiation source outputs radiation and thus generates a three-dimensional radiation field. The radiation has known radiation quantities at every point in the three-dimensional radiation field, whereby the respective point can be unambiguously determined from the known radiation quantities.
The set with a plurality of arrangements for determining a relative position of two objects with respect to one another comprises a plurality of arrangements, whereby each arrangement comprises a radiation source that is configured such that it generates radiation with a characteristic radiation field and comprises a receiver that os configured for the reception of the radiation. The set with a plurality of arrangements further comprises at least one evaluation unit coupled to the receivers with which the relative position of the objects with respect to one another from the signals received from the receiver, said signals being dependent on the reception location in the characteristic radiation field.
The following steps are implemented in the method for determining a relative position of two objects with respect to one another:
a) a radiation source generates radiation with a characteristic radiation field;
b) a receiver measures radiation quantities of the radiation;
c) the receiver transmits signals, which are dependent of the measured radiation quantities in the characteristic radiation field, to the evaluation unit;
d) the evaluation unit determines the relative position of the objects with respect to one another dependent on the signals received by the receiver.
A very simple method and a very simple arrangement for a position sensor are created by the invention. This position sensor makes it possible to simultaneously measure six degrees of motion freedom with only one sensor. The invention additionally permits the miniaturization of such an arrangement. Such a sensor can the be cost-beneficially produced and very flexibly utilized.
Preferred developments of the invention derive from the dependent claims.
The arrangement of radiation source and receiver can ensue in various ways. It has proven advantageous in view of a further simplification of the invention that either the first object carries the radiation source and the second object carries the receiver or the first object carries both the radiation source as well as the receiver. In this case, the second object is equipped with a reflector.
The characteristic radiation field is preferably an asymmetrical radiation field. Simplifications in the interpretation of the radiation quantities derive as a result thereof.
It is provided in a further development that the two objects are connected to one another by an elastic connection having a predetermined stiffness. A force acting between the objects and/or a moment acting between the objects can thus be additionally identified.
For cost reasons, it is advantageous to employ the f
Font Frank G.
Nguyen Sang H.
Siemens Aktiengesellschaft
Staas & Halsey , LLP
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