# US 9,519,281 B2 · System and method for identification of contact between an object and a static implement in a power tool

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- Number: US 9,519,281 B2
- Document ID: US9519281B2
- Status: Granted
- Kind: B2
- Application number: 13/827,606
- Filed: 2013-03-14
- Published: 2014-04-03
- Granted: 2016-12-13
- Earliest claimed: 2012-09-28
- Assignees: Robert Bosch Tool Corporation; Robert Bosch GmbH
- Applicants: Robert Bosch Tool Corporation; Robert Bosch GmbH
- Inventors: Bharadwaja Maharshi Ramaswamy; Niranjan Sathyanarayanarao Krishnarao; Sai Yogesh Kumar Mangapuram; Vishwanatha Manevarthe Srikantiah
- Web page: https://patentgrep.com/patent/US9519281B2

## CPC

- G05B 19/406: characterised by monitoring or safety (G05B19/19 takes precedence)
- B23D 59/001: {Measuring or control devices, e.g. for automatic control of work feed pressure on band saw blade (measuring in general G01; controlling in general G05)}
- B23Q 11/0082: {by determining whether the operator is in a dangerous position (B23Q17/2438 takes precedence)}
- B23Q 17/2438: {of an operator or a part thereof}
- B27G 19/008: {with sensing of human contact or proximity with the blade}
- B27G 21/00: Safety guards or devices specially designed for other wood-working machines {auxiliary devices facilitating proper operation of said wood-working machines}
- G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G)
- B23D: PLANING; SLOTTING; SHEARING; BROACHING; SAWING; FILING; SCRAPING; LIKE OPERATIONS FOR WORKING METAL BY REMOVING MATERIAL, NOT OTHERWISE PROVIDED FOR (making toothed gears or the like B23F; cutting metal by applying heat locally B23K; arrangements for copying or controlling B23Q)
- B23Q: DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING (tools of the kind used in lathes or boring machines B23B27/00); MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
- B27G: ACCESSORY MACHINES OR APPARATUS FOR WORKING WOOD OR SIMILAR MATERIALS; TOOLS FOR WORKING WOOD OR SIMILAR MATERIALS (tools for grinding B24D; sawing tools B27B33/00; tools for slotting or mortising machines B27F5/02; tools for the manufacture of wood shavings, chips, powder or the like B27L11/00); SAFETY DEVICES FOR WOOD WORKING MACHINES OR TOOLS

## Abstract

A method for operating a power tool detects human contact with a non-moving implement of the power tool. The method includes sampling an electrical signal that passes through the non-moving implement, identifying in-phase and quadrature phase components for the sample, identifying a first distance between the components of the sample and a centroid of a cluster of samples corresponding to human contact with the non-moving implement, identifying a second distance between the components of the sample and a second centroid identified for another cluster of samples corresponding to no human contact with the non-moving implement, and identifying human contact with the non-moving implement with reference to the first distance being less than the second distance.

## Claims

### Claim 1

A method for detection of human contact with a non-moving implement in a power tool comprising:
generating a sample of an electrical signal that passes through the non-moving implement;
identifying an in-phase component and quadrature phase component of the sample;
identifying a first distance as a first Pythagorean distance in a two-dimensional plane corresponding to the in-phase and quadrature-phase signals, the first distance being between the identified in-phase component and quadrature phase component of the sample at a first location in the two-dimensional plane and another in-phase component and quadrature phase component of a first centroid at a second location in the two-dimensional plane, the first centroid being of a first cluster of samples in the two-dimensional plane corresponding to human contact with the non-moving implement;
identifying a second distance between the identified in-phase component and quadrature phase component of the sample distance as a second Pythagorean distance in the two-dimensional plane, the second distance being between the first location of the sample and another in-phase component and quadrature phase component of a second centroid at a third location in the two-dimensional plane, the second centroid being of a second cluster of samples in the two-dimensional plane corresponding to no human contact with the non-moving implement; and
identifying human contact with the non-moving implement with reference to the first distance being less than the second distance.

### Claim 2 (depends on 1)

The method of claim 1 further comprising:
disabling operation of an actuator in the power tool that is configured to move the implement in response to identifying the human contact with the non-moving implement.

### Claim 3 (depends on 1)

The method of claim 1 further comprising:
operating an actuator in the power tool to move the implement in response to the second distance being less than the first distance.

### Claim 4 (depends on 1)

The method of claim 1 further comprising:
electrically coupling the electrical signal into the non-moving implement of the power tool;
sampling the electrical signal to obtain the first cluster of samples of the electrical signal electrically coupled to the non-moving implement during a first time period during which human contact with the non-moving implement occurs;
sampling the electrical signal to obtain the second cluster of samples of the electrical signal electrically coupled to the non-moving implement during a second time period during which no human contact with the non-moving implement occurs;
identifying the first centroid for the multiple samples of the electrical signal obtained during the first time period;
identifying the second centroid for the multiple samples of the electrical signal obtained during the second time period; and
storing the first centroid and the second centroid in a memory within the power tool for detection of human contact with the non-moving implement.

### Claim 5 (depends on 4)

The method of claim 4, the sampling of the electrical signal further comprising:
identifying an in-phase component for each sample of the electrical signal during the first time period and the second time period; and
identifying a quadrature component for each sample of the electrical signal during the first time period and the second time period.

### Claim 6

A power tool comprising:
an actuator configured to move an implement;
a clock source configured to generate a time varying electrical signal that passes through the implement; and
a controller operatively connected to the actuator and configured to sample the electrical signal, the controller being configured to:
generate a sample of the electrical signal when the actuator is deactivated and the implement is a non-moving implement;
identify an in-phase component and quadrature phase component of the sample;
identify a first distance as a first Pythagorean distance in a two-dimensional plane corresponding to the in-phase and quadrature-phase signals, the first distance being between the identified in-phase component and quadrature phase component of the sample at a first location in the two-dimensional plane and another in-phase component and quadrature phase component of a first centroid at a second location in the two-dimensional plane, the first centroid being of a first cluster of samples corresponding to human contact with the non-moving implement;
identify a second distance as a second Pythagorean distance in the two-dimensional plane, the second distance being between the first location of the sample and another in-phase component and quadrature phase component of a second centroid at a third location in the two-dimensional plane, the second centroid being of a second cluster of samples corresponding to no human contact with the non-moving implement; and
identify human contact with the non-moving implement with reference to the first distance being less than the second distance.

### Claim 7 (depends on 6)

The power tool of claim 6 further comprising:
a memory operatively connected to the controller, the memory being configured for storage of data corresponding to the in-phase component and the quadrature phase component of the first centroid and the in-phase component and the quadrature phase component of the second centroid prior to the generation of the sample.

### Claim 8 (depends on 6)

The power tool of claim 6 further comprising:
an activation switch operatively connected to the controller, the controller being further configured to:
identify the human contact with the non-moving implement in response to operation of the activation switch.

### Claim 9 (depends on 6)

The power tool of claim 6, the controller being further configured to:
disable the actuator in response to identifying the human contact with the non-moving implement.

### Claim 10 (depends on 6)

The power tool of method of claim 6, the controller being further configured to:
operate the actuator to move the implement in response to the second distance being less than the first distance.