An　adaptive　dynamic　vibration　absorber　(ADVA)　is　designed　for　low-frequency　vibration　suppression.　The　leaf　springs　are　applied　as　the　tuning　stiffness　elements.　The　principle　of　variable　stiffness　is　analyzed　to　obtain　the　effective　range　of　the　first　natural　frequency　variation.　A　classic　simply　supported　manipulator　is　selected　as　the　controlled　system.　The　coupled　dynamic　model　of　the　manipulator-ADVA　system　is　built　to　obtain　the　maximum　damping　efficiency　and　the　vibration　absorption　capacity　of　the　designed　ADVA.　An　experimental　platform　is　set　up　to　verify　the　theoretical　results.　It　is　revealed　that　the　ADVA　can　adjust　the　first　natural　frequency　on　a　large　scale　by　changing　the　curvature　of　the　leaf　springs.　The　amplitude　of　the　manipulator　is　reduced　obviously　with　the　installation　of　the　designed　ADVA.　Finally,　based　on　the　short-time　Fourier　transformation　(STFT),　a　stepwise　optimization　algorithm　is　proposed　to　achieve　a　quick　tuning　of　the　natural　frequency　of　the　ADVA　so　that　it　can　always　coincide　with　the　frequency　of　the　prime　structure.　Through　the　above　steps,　the　intelligent　frequency　tuning　of　the　ADVA　is　realized　with　high　vibration　absorption　performance　in　a　wide　frequency　range.