Atomic & Space Age (1940–1970)Robotics, Teleoperation & Servo Control

Goertz Force-Reflecting Master–Slave Manipulator

US 2,846,084

Seven coordinated motion channels, synchro error control, and bilateral resistance

Inventor(s)Raymond C. Goertz, William M. Thompson, Robert A. Olsen

Grant DateAugust 5, 1958

Filing DateJune 21, 1955

LocationDowners Grove and Chicago, Illinois

This Atomic Energy Commission grant claims an electrical master–slave manipulator in which a human-operated handle and a remote claw correspond through seven motion-specific assemblies. Synchro transducers form a position-error signal, reversible motors drive both sides toward correspondence, tachometer feedback damps relative motion, and a limiter bounds excessive error signals. Its claims distinguish this particular bilateral arm-and-servo architecture from a generic claim to every robot or remote-control system.

USPTO PDF

Engineering Analysis & Physical Principles

How It Works: Step-by-Step Mechanical & Physical Breakdown

This is an early bilateral teleoperation architecture for a job that cannot safely put a person at the work site. A human moves a master handle; a remote slave claw follows. The important refinement is not merely remote motion: each of seven source-described movements has a corresponding position-error servo channel, and an obstacle at the claw raises the error that pushes back at the master. The patent therefore treats delicate remote work as a problem of kinematics, feedback, damping, cable management, and force reflection together.

The Core Breakthrough Mechanism

For one motion channel, let $q_m$ be the master position and $q_s$ the slave position. The synchro pair produces an error signal with $E \propto q_m-q_s$ ; phase carries direction. The amplifier drives reversible motors in the direction that reduces the mismatch, while a tachometer path opposes relative speed, $V_t \propto \dot q_m-\dot q_s$ . If the slave claw contacts an object, $q_s$ cannot advance with $q_m$ , so $|E|$ increases and the master motor opposes the operator. That is a real closed-loop causal chain. The grant supplies no arm lengths, gear ratios, payload, contact stiffness, motor constants, control gains, or bandwidth, so the shared interactive model intentionally reports normalized motion and resistance relationships rather than invented SI force or performance values.

Interactive Real-Time Physical Simulation

Drag to rotate · Scroll to zoom · Shared controls update the displayed modelDrag to rotate · Pinch to zoom · Shared controls update the displayed model

INITIALIZING THREE.JS WEBGL SIMULATION...

Host-Model Telemetry/Computed Readout

Bilateral Teleoperation & Force-Reflecting Servo Topology

Master Channel Commands

Normalized

0.18 · -0.12 · 0.22 · 0.08 · -0.15 · 0.11 · 0.307 normalized channels[1]

Illustrative Remote Obstruction

Reader Scenario

0.45normalized reader scenario[1]

Largest Channel Mismatch

Normalized

9% normalized[1]

Reflected Resistance

Normalized

9% normalized[1]

Servo State

Source

FORCE-REFLECTING REMOTE CONTACTsource topology[1]

Feedback / Limiter Path

Source

DAMPED · LIMITINGsource topology[1]

Claim Probe

Source

CLAIM 11issued text[1]

Quantitative SI Prediction

Source Refusal

REFUSEDmissing source inputs[1]

Horizontal Arm Pivot · Axis 113b+0.18 normalized

Horizontal Arm Roll-0.12 normalized

Vertical Arm Pivot · Axis 126+0.22 normalized

Vertical Arm Roll+0.08 normalized

Tool Pivot · Axis 171-0.15 normalized

Tool Pivot · Axis 172+0.11 normalized

Tool Closure0.3 normalized

Remote Contact Resistance0.45 illustrative normalized state

Claim 9 Force Reflection1 off/on

Claim 11 Tachometer Path1 off/on

Claims 10/12 Limiter1 off/on

Detailed Component Architecture

1Seven mechanically distinct motion channels

The master and slave have first and second arms plus a tool, with seven movements reproduced through seven corresponding assemblies.

The source enumerates pivoting the horizontal arm about transverse axis $113b$ and its own axis, pivoting the vertical arm about axis $126$ and its own axis, two tool-axis pivots $171$ and $172$ , and opening or closing the tool. A configuration vector $q=(q_1,\ldots,q_7)$ makes that architecture legible. It does not supply a calibrated coordinate frame or link dimensions, so the exhibit uses normalized channel positions only.

19th-C. Term: master unit and slave unitModern: bilateral teleoperation master and remote manipulator

2Handle, claw, and cable paths

The master tool is a hand-held handle; the slave tool is a claw or grasper. Flexible cable routes carry several tool motions through the arms.

Cables $160$ through $164$ route gripping and tool-axis motions through the vertical and horizontal arms to assemblies $54$ through $56$ ; cables $175$ and $176$ route vertical-arm rotation to assembly $57$ . Pulleys, take-up sheaves, and spring-loaded gear boxes manage changes in path length when a different joint moves. This is a source-backed routing topology, not a quantified cable-stress calculation.

19th-C. Term: force-receiving and -transmitting assembliesModern: motion-channel transmission and servo packages

3Synchro position correspondence

A master-side synchro control transformer and slave-side synchro transmitter turn angular mismatch into a direction-sensitive alternating error signal.

The grant says the error signal $E$ is proportional in amplitude to the difference between corresponding shaft positions and that its phase indicates the direction of mechanical error. In modern control notation, $E\propto q_m-q_s$ . That relationship determines direction and relative correction demand, but the source does not publish a volts-per-degree conversion or servo gain.

19th-C. Term: synchro control transformerModern: electromechanical position-error transducer

4Force-reflecting motor pair

Reversible motors act on both sides of a channel so a slave obstruction produces resistance at the master handle.

Claim 9 is not a generic haptics slogan. It requires corresponding movable elements, an error signal responsive to slave-versus-ideal position, and forces tending to reduce the mismatch on both master and slave. The beaker example illustrates $q_s$ lagging because contact prevents further closure; the rising $|E|$ drives a corresponding opposing motor action at the master. No force-newton output is asserted because force calibration and contact mechanics are absent from the grant.

19th-C. Term: sense of feelModern: bilateral force reflection / haptic feedback

5Tachometer damping and abnormal-condition limiter

Relative motor-speed feedback opposes fast mismatch changes, while a limiter restricts excessively large error signals.

The tachometer bridge produces a signal proportional to a speed difference and opposes it against the position-error signal: $V_t\propto\dot q_m-\dot q_s$ . Claims 10–12 add signal limiting and speed-difference feedback. The document prints examples of components and a 60-cycle motor arrangement, but not a universal closed-loop transfer function, stability margin, maximum velocity, or safety rating.

19th-C. Term: signal-limiting meansModern: command-amplitude limiter with derivative-like damping path

Engineering Principles & Equations

Governing Equations & Engineering Principles

Authored explanation paired with its stated mathematical relation

Synchro Position-Error Correspondence

Source-Bounded Bilateral TeleoperationClaim 9

Mathematical Governing Law

\htmlClass{eq-term eq-term-position_error eq-term-amber}{\htmlData{var=position_error}{\textcolor{#f59e0b}{E}}}\propto\htmlClass{eq-term eq-term-master_position eq-term-cyan}{\htmlData{var=master_position}{\textcolor{#06b6d4}{q_m}}}-\htmlClass{eq-term eq-term-slave_position eq-term-amethyst}{\htmlData{var=slave_position}{\textcolor{#8b5cf6}{q_s}}}

Terms:

Plain English DecoderHover or tap any highlighted phrase

The source-described synchro pair makes an from the difference between the normalized master and its corresponding slave .

E

Synchro Position-Error Signal

The source’s directional alternating error signal between corresponding positions

normalized source topology[1]

The grant says amplitude is proportional to the difference and phase records the direction of mechanical error. It does not publish a volts-per-degree conversion or loop gain.

Live Physical Value:

9 % normalized

Physical Principle & Engineering Insight

This is a source-level proportionality statement, not a fabricated controller equation. The visitor can vary a named master channel and an illustrative contact state, but the document does not justify numerical voltage, gain, speed, force, or bandwidth output.

Historical Context: Claim 9 makes position difference the bridge between remote obstruction and a response on both members of a bilateral master–slave system.

Claim 9 Reflected-Resistance Relationship

Source-Bounded Bilateral TeleoperationClaim 9

Mathematical Governing Law

\htmlClass{eq-term eq-term-reflected_resistance eq-term-emerald}{\htmlData{var=reflected_resistance}{\textcolor{#059669}{r_{\text{display}}}}}\propto|\textcolor{#f59e0b}{E}|

Terms:

Plain English DecoderHover or tap any highlighted phrase

When the remote mechanism meets an illustrative , the rising mismatch produces a normalized when Claim 9 force reflection is enabled.

r_{\text{display}}

Reflected-Resistance Display

Normalized visual indicator of the source-described resistance returning to the master

normalized display relation[1]

It is deliberately not labelled newtons or torque. The historical patent says resistance can appear at the master but does not give a force calibration, impedance, or contact model.

Live Physical Value:

9 % normalized

Physical Principle & Engineering Insight

The equation intentionally uses a display relation rather than a force law. It makes the beaker example legible while preserving the boundary between a historical bilateral-servo claim and an unprovided Newton-for-Newton haptic calibration.

Historical Context: The issued language is an early clear statement that remote mechanical resistance can be returned to a human operator through a paired electrical servo arrangement.

Relative-Speed Feedback and Limited Error Path

Source-Bounded Bilateral TeleoperationClaim 12

Mathematical Governing Law

\htmlClass{eq-term eq-term-tachometer_signal eq-term-amethyst}{\htmlData{var=tachometer_signal}{\textcolor{#9333ea}{V_t}}}\propto\dot{\textcolor{#06b6d4}{q_m}}-\dot{\textcolor{#8b5cf6}{q_s}},\qquad\htmlClass{eq-term eq-term-drive_error eq-term-amber}{\htmlData{var=drive_error}{\textcolor{#f59e0b}{E_{\text{drive}}}}}=\operatorname{limit}(\textcolor{#f59e0b}{E}-\htmlClass{eq-term eq-term-tachometer_signal eq-term-amethyst}{\htmlData{var=tachometer_signal}{\textcolor{#9333ea}{V_t}}})

Terms:

Plain English DecoderHover or tap any highlighted phrase

The source’s tachometer path opposes a against the position error, while its bounds abnormal-condition command amplitude.

V_t

Relative-Speed Feedback Signal

Source-described tachometer bridge output responsive to a difference in motor speeds

topology state[1]

The patent says the path opposes the error-signal path to reduce oscillation. It supplies neither a calibrated velocity measurement nor a frequency-response model.

Live Physical Value:

1.00 topology state

Physical Principle & Engineering Insight

Claims 10–12 add real control-architecture ideas—limiting and speed-difference opposition—without providing the numbers needed to simulate a physical motor loop. The live system labels those boundaries rather than creating false dynamics.

Historical Context: These dependent claims capture a historically early combination of bilateral position correspondence, bounded abnormal-condition response, and relative-speed damping.

Bilateral position errorAuthored Principle 1

Stated relation

E \propto q_m-q_s

The synchro pair creates a signal whose amplitude is proportional to the mismatch between a master channel and its corresponding slave channel, while phase indicates correction direction. The proportionality is source-supported; its numerical gain is not published.

Force reflection through matched correctionAuthored Principle 2

Stated relation

\tau_m,\tau_s \propto E

Claim 9 directs force to both movable elements in a way that tends to reduce their positional disagreement. The source’s beaker example explains why an obstruction then becomes resistance at the master; it does not establish a Newton-for-Newton calibration.

Relative-speed dampingAuthored Principle 3

Stated relation

V_t \propto \dot q_m-\dot q_s, \qquad E_{drive}=E-kV_t

The tachometer bridge makes an electrical signal from a difference in corresponding motor speeds and opposes it against the position-error path. The second expression is a modern sign convention for the stated opposing relationship, not an unpublished controller-gain value.

Seven-axis configuration topologyAuthored Principle 4

Stated relation

q=(q_1,q_2,q_3,q_4,q_5,q_6,q_7)

The vector labels the seven movements actually enumerated in the specification. It helps distinguish the individual correspondence channels from a made-up Cartesian workspace or geometric performance envelope.

Amplitude limitingAuthored Principle 5

Stated relation

u=\operatorname{limit}(E)

Claims 10 and 12 require a signal-limiting means used to limit device speed under abnormal conditions. The notation communicates bounded command amplitude without suggesting that the patent supplies a threshold, rated torque, or certified safety limit.

Interactive Schematic Sheet (Fig. 1)

The source elevation identifies the support, horizontal and vertical arms, tool, and motion assemblies of the master unit.

1.00x

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Why It Still Matters

The patent makes a useful historical distinction that still matters in robotics: remote manipulation is not solved by sending position alone. A practical operator needs a structured arm, transmission paths that survive multi-axis motion, stable tracking, and a way for remote resistance to return to the hand. The architecture belongs to the lineage of nuclear hot-cell manipulators and later force-reflecting teleoperation. Modern surgical, underwater, and hazardous-environment systems use far newer electronics and safety practice, but they confront the same separation between commanded motion, remote contact, and human perception.

Legal Claims Decoder (13 Numbered Claims)

Compare dense legalistic claims directly with decoded plain-English functional specifications.

Claim #1Independent Master Claim

1/13

Verbatim Historical Legal Text

“A remote-control manipulator comprising a master unit and a slave unit; each unit comprising a first arm having inner and outer ends, means mounting said first arm for angular movement about its own axis and about an axis perpendicular thereto at said inner end, a second arm having inner and outer ends, means connecting the inner end of the second arm with the outer end of the first arm for causing the second arm to have conjoint angular movement with the first arm about the axis of the latter and for enabling the second arm to have angular movement with respect to the first arm about an axis perpendicular to the axis of the first arm at the outer end thereof, a tool, and means mounting the tool on the outer end of the second arm for angular movement about the axis of the second arm and about two more axes angularly related to the axis of the second arm and extending through the outer end of the second arm in angular relationship to one another; means for producing electrical signals responsive to the aforesaid angular movements of the first and second arms and the tool of the one unit and to opening and closing of the tool thereon; and means responsive to said signals for producing corresponding angular movements of the first and second arms and the tool of the other unit and opening and closing of the tool thereon.”

Plain English Engineering Translation

Claim 1 is the broad arm-and-signal combination. It requires corresponding master and slave units, two articulated arms, a tool with three angular relations, electrical signals for those motions and tool opening or closing, and a response that reproduces them remotely. It does not read simply on any two robotic arms, because the specified multi-axis structure and signal-responsive correspondence are both doing legal work.

Key Protected Innovations:

Corresponding master and slave armsThree-axis tool mountingElectrical motion correspondenceTool opening and closing channel

Historical Legal Impact:

This is the broadest issued structural formulation of the paired articulated manipulator and its electrically reproduced motions.

The Historical Bottleneck

A worker needs to grasp, orient, and move objects in a remote or sealed environment where direct access is unsafe or impossible, without losing the tactile judgment that prevents damaging fragile objects or pushing into an obstruction.

Why Prior Art Failed

•A direct mechanical linkage ties master and slave separation, routing, and enclosure design together.
•Sending motion alone can make a remote claw follow while withholding resistance at the work site from the operator’s hand.
•Multi-axis cable paths can change length when another joint moves, creating slack, excess tension, or entanglement unless their geometry is managed.
•An error-driven servo can oscillate or overdrive a motor unless relative-speed feedback and abnormal-condition limiting are designed into the control path.

The Breakthrough Insight

“The grant joins an articulated, cable-managed arm to a repeated bilateral servo channel: position mismatch produces an electrical correction signal, and a remote obstruction converts that mismatch into opposing action at the operator’s handle. It gives a mechanical form to the idea that remote manipulation must carry both motion and resistance.”

After the Grant

Historical accounts of nuclear remote handling describe the Goertz electrical master–slave architecture as a significant transition from direct mechanical linkages to systems with much greater separation and flexible installation. The record is careful not to convert that broader deployment history into an unproved sales or performance claim for this single patent.

Civilizational Impact

The electronic master–slave approach became part of the technical lineage of manipulators used around nuclear hot cells and other hazardous environments. Its enduring educational value is not a claim that every later robot descends legally from this grant; it is the unusually explicit demonstration that useful teleoperation is a coupled mechanics-and-feedback problem.

Historical Fact

The specification uses closing a remote claw on a glass beaker as its intuitive test case for force reflection: once the claw touches the beaker, the rising position mismatch causes resistance at the operator’s handle.