{
  "$type": "site.standard.document",
  "description": "A method of operating a piezoelectric actuator including a stack (14) of one or more elements of piezoelectric material comprises the following steps: at a first time (i) varying the charge across the stack between a first positive charge level (+Q1) and a first negative charge level (-Q2) so as to…",
  "path": "/patents/1084929",
  "publishedAt": "2004-08-11T00:00:00.000Z",
  "site": "at://did:plc:oql6ds5vnff4ugar6rruliwd/site.standard.publication/3mn3ohu7oxx5w",
  "tags": [
    "F02D41/2096",
    "DELPHI TECH INC [US]"
  ],
  "textContent": "A method of operating a piezoelectric actuator including a stack (14) of one or more elements of piezoelectric material comprises the following steps: at a first time (i) varying the charge across the stack between a first positive charge level (+Q1) and a first negative charge level (-Q2) so as to displace the stack (14) through a first amount (Z1) (ii) measuring a first charge difference between the first positive charge level (+Q1) and the first negative charge level (-Q2) and (iii) determining a first operating characteristic (dV/dQ; dQ/dV) of the actuator, and subsequently, at a later time, varying the charge across the stack (14) between a second positive charge level (+Q3) and a second negative charge level (-Q4) so as to displace the stack (14) through a second amount (Z2). The second positive and negative charge levels (+Q3, -Q4) are selected in dependence upon the first operating characteristic (dV/dQ; dQ/dV) and such that the difference between the second positive charge level (+Q3) and the second negative charge level (-Q4) is substantially the same as the first charge difference, thereby to ensure the second amount (Z2) through which the actuator is displaced is substantially the same as the first amount (Z1).",
  "title": "Control method for a piezoelectric actuator"
}