Power-assisted bicycle with a gear shift smoothening function

A power-assisted bicycle, comprising:

• a bicycle body comprising a power assistance provider and a derailleur;
• a microcomputer electrically coupled with said power assistance provider and adapted for controlling said power assistance provider to provide an assistant power output;
• a gear-shift control driver electrically connected to said microcomputer and physically connected to said derailleur for driving said derailleur to shift gears subject to the control of said microcomputer;
• at least one sensor mounted at said bicycle body at a respective selected location and electrically connected to said microcomputer for sensing at least one of the conditions of wheel speed, pedaling speed, pedaling force and slope and providing at least one sensing signal for causing said microcomputer to generate at least one detection result and to determine gearshift timing subject to said at least one detection result, said at least one sensor including at least one of a wheel speed sensor and a pedaling speed sensor;
• and
• wherein when the wheel speed meets a first condition or the pedaling speed meets a second condition during the operation of said microcomputer to judge gearshift timing, said microcomputer divides the time period of the gear-shifting process into a before-shifting time period, an in-shifting time period and an after-shifting time period, and controls said power assistance provider to provide an assistant power output and said gear-shift control driver to drive said derailleur to shift gears during the three time periods of before-shifting time period, in-shifting time period and after-shifting time period;
• and
• wherein:
• said microcomputer controls said power assistance provider to change the current assistant power output thereof to a predetermined low assistant power during said before-shifting time period;
• said microcomputer controls said power assistance provider to maintain said predetermined low assistant power and said gear-shift control driver to drive said derailleur to shift gears during said in-shifting time period;
• said microcomputer controls said power assistance provider to change the assistant power output from said predetermined low assistant power to a level higher than the current assistant power output thereof when gearing up during said after-shifting time period, and then controls said power assistance provider to return the assistant power output to said current assistant power output after the end of said after-shifting time period;
• said microcomputer controls said power assistance provider to change the assistant power output from said predetermined low assistant power to said current assistant power output when gearing down during said after-shifting time period.