Power tool compensator for torque overshoot

A method for compensating for torque overshoot in a rotary power tool wherein the tool is to be shut off at a target torque and is actually shut off at a torque set point equal to or less than the target torque depending upon the amount of torque overshoot, said method comprising the steps of:

• (a) operating the tool to perform a first fastening job;
• (b) measuring time duration between selected fractions of the target torque which occur during a portion of the fastening job when the torque rate is linear to provide a fastener deceleration time value;
• (c) determining the torque overshoot by subtracting the measured torque at the end of the fastening job from the target torque;
• (d) calculating a value of K from an expression K=XY where Y is torque overshoot and X is deceleration time required to tighten the fastener;
• (e) operating the tool to perform a second fastening job;
• (f) measuring the time duration between the same selected fractions of target torque as in the first measuring step to obtain a deceleration time for said second fastening job;
• (g) determining torque overshoot for said second fastening job from an expression Y=K/X using the value of K determined during said first fastening job and the deceleration time obtained during said second fastening job;
• (h) determining a new torque set point according to a relationship
• S=[(Target)/(Target+Y)](Target)
• where S is the new set point, Target is the target torque and Y is the torque overshoot determined for the second fastening job;
• and
• (i) establishing a running average of the constant K.

A method for compensating for torque overshoot in a power tool wherein the tool is to be shut off at a target torque and is actually shut of at a torque set point equal to or less than the target torque depending upon the amount of torque overshoot, said method comprising the steps of:

• (a) operating the tool to perform a high torque rate fastening job;
• (b) measuring torque angle between selected fractions of the target torque which occur during a portion of the fastening job when the torque rate is linear to provide a fastener deceleration angle value;
• (c) measuring the torque overshoot on the job;
• (d) calculating a value of K from an expression K=XY where Y is torque overshoot and X is a deceleration angle required to tighten the fastener;
• (e) operating the tool to perform a next fastening job;
• (f) measuring the torque angle between the same selected fractions of target torque as in the first measuring step to obtain a deceleration angle for said next fastening job;
• (g) determining the torque overshoot for said next fastening job from the expression Y=K/X using the value of K previously determined and a value of X measured during said next fastening job;
• and
• (h) adjusting the torque set point to compensate for the calculated valve of overshoot.

A system for compensating for torque overshoot in a rotary power tool including control means to normally shut off the tool at a target torque and to actually shut off the tool at a torque set point equal to or less than the target torque depending upon the amount of torque overshoot, said system comprising:

• (a) torque measuring means operatively associated with said tool for providing an output indicative of the torque of said tool;
• (b) processor means having an input operatively connected to said torque measuring means and having an output operatively connected to said control means;
• and
• (c) said processor means including means for computing deceleration time between selected fractional values of the target torque, means for computing the torque overshoot, means operatively connected to said means for computing deceleration time and to said means for computing overshoot for computing a constant K in a relationship K=XY where Y is computer overshoot and X is computer deceleration time, the constant K being determined by using values of overshoot and deceleration time during a previous high torque-rate application of said tool, and means connected to said means for computing K and to said means for computing deceleration time for computing overshoot according to the relationship Y=K/X so that the output of said means for computing overshoot is used for adjusting the torque set point via said control means to compensate for the computed value of torque overshoot.

A method for compensating for torque overshoot in a rotary power tool wherein the tool is to be shut off at a target torque and is actually shut off at a torque set point equal to or less than the target torque depending upon the amount of torque overshoot, said method comprising the steps of:

• (a) operating the tool to perform a fastening job;
• (b) determining a relationship between torque rate in the fastening job to overshoot in the tool while the tool is performing the job;
• (c) monitoring the torque rate in the job while the tool is setting the job;
• (d) measuring deceleration time and torque overshoot during the job, said deceleration time being measured between selected fractional values of the target torque;
• (e) adjusting the torque set point while the tool is setting the job to compensate for overshoot related to the torque rate according to said relationship between torque rate and overshoot;
• (f) said relationship between torque rate in the fastening job to overshoot in the tool following the mathematical expression Y=K/X where Y is overshoot, X is deceleration time required to tighten the fastener and K is a constant which is determined by using the measured deceleration time and torque overshoot during a previous fastening job in said expression;
• and
• (g) during a subsequent fastening job, measuring deceleration time between the same selected fractional values of target torque of a previous high torque-rate job, calculating overshoot from the foregoing mathematical expression using the previously determined value of K, and adjusting the torque set point to compensate for the calculated value of overshoot.

A method for compensating for torque overshoot in a rotary power tool wherein the tool is to be shut off at a target torque and is actually shut off at a torque set point equal to or less than the target torque depending upon the amount of torque overshoot, said method comprising the steps of:

• (a) operating the tool to perform a fastening job;
• (b) determining a relationship between torque rate in the fastening job to overshoot in the tool while the tool is performing the job;
• (c) monitoring the torque rate in the job while the tool is setting the job;
• (d) measuring deceleration angle and torque overshoot during the job, said deceleration angle being measured between selected fractional values of the target torque;
• (e) adjusting the torque set pint while the tool is setting the job to compensate for overshoot related to the torque rate according to said relationship between torque rate and overshoot;
• (f) said relationship between torque rate in the fastening job to overshoot in the tool following the mathematical expression Y=K/X where Y is overshoot, X is deceleration angle required to tighten the fastener and K is a constant which is determined by using the measured deceleration angle and torque overshoot during a previous fastening job in said expression;
• and
• (g) during a subsequent fastening job, measuring deceleration angle between the same selected fractional values of target torque of a previous high torque-rate job, calculating overshoot from the foregoing mathematical expression using the previously determined value of K, and adjusting the torque set point to compensate for the calculated value of overshoot.