Cmr Surgical Limited

Cadence Design Systems, Inc.

Edward John Mottram

Paul Christopher Roberts

Gordon Thomas Deane

Graham John Veitch

Edward Tucker

Keith Marshall

Thomas Bates Jackson

Ricardo Michael Henderson Da Silva

Andrew Murray Scholan

Edward James Wildin Tucker

Matthew David Eaton

A method for controlling a mechanical system having a plurality of components interlinked by a plurality of driven joints, the method comprising: measuring torques or forces about or at the driven joints and forming a load signal representing the measured torques or forces; receiving a motion demand signal representing a desired state of the system; implementing an impedance control algorithm in dependence on the motion demand signal and the load signal to form a target signal indicating a target configuration for each of the driven joints; measuring the configuration of each of the driven joints and forming a state signal representing the measured configurations; and forming a set of drive signals for the joints by, for each joint, comparing the target configuration of that joint as indicated by the target signal to the measured configuration of that joint as indicated by the state signal.

Robot control

A method for limiting joint velocity of a plurality of joints of a surgical robotic system, the surgical robotic system comprising a robot having a base and an arm extending from the base to an attachment for an instrument, the arm comprising a plurality of joints whereby the configuration of the arm can be altered, the method comprising: obtaining joint states for a first group of k joints of the arm, where k>1; for each of the k joints: determining from the obtained joint state a permitted range of motion for that joint; deriving, using the permitted range of motion, a joint velocity limit for that joint; selecting the minimum joint velocity limit of the k joints to be a common joint velocity limit used to limit each of the k joints individually; and calculating drive signals for driving the k joints wherein the velocity of each of the k joints is limited using the common joint velocity limit.

Robotic joint control

A circuit for sensing the driving current of a motor, the circuit comprising: a driver configured to generate a driving current for each phase of a multiple-phase motor, the instantaneous sum of all the driving currents being zero; a current sensor for each phase of the multiple-phase motor, each current sensor configured to measure the driving current of that phase and comprising a plurality of current sensor elements arranged with respect to each other such that each current sensor element has the same magnitude of driving current systematic error due to magnetic fields external to the driving current to be measured; and a controller configured to, for each phase of the multiple-phase motor, generate an estimate of the driving current of that phase to be the measured driving current of that phase minus 1/n of the total of the measured driving currents for all phases, n being the number of phases of the multiple-phase motor.

Sensing motor current

Aspects of the disclosure include a torque sensor arrangement configured to attach between a first part and a second part to sense torque therebetween, the torque sensor arrangement comprising an interface member having on its exterior an engagement configuration configured to rotationally engage the first part, a torsion member comprising a deflectable body attached at one end thereof to the interface member and comprising, at the other end of the deflectable body, an engagement configuration configured to fixedly engage the second part, and a deflection sensor attached to the deflectable body, wherein the interface member defines a rigid sleeve extending around the deflectable body and the torque sensor arrangement further comprises a bushing located between and in contact with both the sleeve and the deflectable body.

Torque sensor

A position sensing arrangement for sensing the position of a revolute joint of an articulated structure. The position sensing arrangement comprises a disc and a magnetic sensor assembly. The disc comprises a first magnetic ring with m magnetic pole pairs, and a second magnetic ring with n magnetic pole pairs, where m and n are co-prime, and a mounting arrangement by which the disc is mountable to a magnetisation jig during manufacture and the articulated structure during operation, the mounting arrangement permitting the disc to be mounted to the magnetisation jig and articulated structure in a single orientation only. The magnetic sensor assembly comprises a first magnetic sensor array for detecting the magnetic pole pairs of the first magnetic ring, and a second magnetic sensor array for detecting the magnetic pole pairs of the second magnetic ring.

Magnetic position sensor mounting arrangement

A method of assembling a position sensing arrangement for sensing the position of a revolute joint of an articulated structure. The position sensing arrangement comprises a magnetic sensor assembly and a disc having a first magnetic ring with j magnetic pole pairs and a second magnetic ring with k magnetic pole pairs. A boundary of the disc is constrained by the articulated structure. The method comprises: determining a number of pole pairs of the first magnetic ring to be an integer p such that the first magnetic ring is separated from the constrained boundary by at least the magnetic sensor assembly; determining a number of pole pairs of the second magnetic ring to be an integer q such that the second magnetic ring is separated from the first magnetic ring by a predetermined distance; and if p and q are co-prime: selecting j to be p and k to be q; and assembling the position sensing arrangement by mounting the disc to the articulated structure such that both the disc and the revolute joint are permitted to rotate about the same axis.

Magnetic position sensor for sensing position of a revolute joint

For a division of a dividend by a constant divider, a circuit architecture may calculate partial remainders. The circuit architecture may implement a tree structure to generate intermediate signals of partial remainders and combine adjacent intermediate signals to generate other partial remainders downstream. The circuit architecture may generate a quotient based on the partial remainders. The circuit architecture may also implement bit shifting and zero-padding on left side of the dividend to generate bit-level partial remainders. Furthermore, the circuit architecture may enable a fast round-to-zero division of signed integers by flipping the input bits of a negative integer and output bits of the corresponding quotient and performing only one increment operation, either before the division or after the division. In addition, the circuit architecture may also perform a division of a dividend in a carry-save form.

Systems and methods for synthesizing a circuit architecture for division by constants

A method of correcting a position reading from a position sensing arrangement. The position sensing arrangement is suitable for sensing the position of a revolute joint of an articulated structure, and comprises a disc having a magnetic ring with magnetic pole pairs and a magnetic sensor assembly comprising a magnetic sensor array for detecting the magnetic pole pairs of the magnetic ring. The method comprises: for each pole pair of the magnetic ring, taking a calibration pole pair position reading with the magnetic sensor array, and generating a pole pair correcting function by comparing the calibration pole pair position reading with a model pole pair position reading; averaging the pole pair correcting functions of the pole pairs of the magnetic ring to generate an average pole pair correcting function for the magnetic ring; taking a position reading with the magnetic sensor array, the position reading comprising a plurality of pole pair position readings; and generating a corrected position reading by deducting the average pole pair correcting function from each pole pair position reading.

Calibrating position sensor readings

A robot arm comprising a joint mechanism for articulating one limb () of the arm relative to another limb () of the arm about two non-parallel rotation axes (), the mechanism comprising: an intermediate carrier () attached to a first one of the limbs by a first revolute joint having a first rotation axis and to a second one of the limbs by a second revolute joint having a second rotation axis; a first drive gear () disposed about the first rotation axis and fast with the carrier, whereby rotation of the carrier relative to the first limb about the first rotation axis can be driven; a second drive gear () disposed about the second rotation axis and fast with the second one of the limbs, whereby rotation of the second one of the limbs about the second rotation axis relative to the carrier can be driven; at least one of the first and second drive gears being a sector gear.

Gear packaging for robot arms

A robot arm having a compound joint between a first limb of the arm and a second limb of the arm, the second limb of the arm being distal of the first limb, the arm comprising: a coupler element coupled to the first limb of the arm by a first revolute joint having a first rotation axis and to the second limb of the arm by a second revolute joint having a second rotation axis; first and second rotational position sensors for sensing the configuration of the arm about the first and second joints respectively; first and second torque sensors for sensing the torque applied about the first and second joints respectively; a control unit for controlling the operation of the arm; a first communications unit borne by the arm and located proximally of the coupler and a second communications unit borne by the arm and located distally of the coupler, each communications unit being capable of encoding data received from one or more of the position and/or torque sensors in a first data format into data packets and transmitting those packets to the control unit in accordance with a packet-based data protocol different from the first data format; wherein the first position sensor is connected by a physical data link running within an exterior wall of the first limb to the first communications unit to so as to pass data representing sensed position about the first joint to the first communications unit for encoding and the first torque sensor is connected by a physical data link running within an exterior wall of the second limb to the second communications unit to so as to pass data representing sensed torque about the first joint to the second communications unit for encoding.

Growing community of inventors

Cambridge, United Kingdom

Edward John Mottram